lots of progress, including readonly PATA driver and part of FAT16 driver

27 files changed, 285 insertions, 274 deletions

diff --git a/makefile b/makefile
index 03ab19a..2152dde 100644
--- a/makefile
+++ b/makefile
@@ -21,7 +21,7 @@ skel:
 	mkdir -p out/fs
 	cp -r fs-skel/* out/fs/
 
-kgccargs = -Wall -m32 -Og -ffreestanding -fno-asynchronous-unwind-tables
+kgccargs = -Wall -Wsuggest-attribute=pure -Wsuggest-attribute=const -Wsuggest-attribute=malloc -m32 -Og -ffreestanding -fno-asynchronous-unwind-tables
 ugccargs = ${kgccargs} -Isrc/libc/inc
 nasmargs = -f elf32
 
diff --git a/src/kernel/ata.h b/src/kernel/ata.h
index 7c42cdb..28ef0de 100644
--- a/src/kernel/ata.h
+++ b/src/kernel/ata.h
@@ -38,23 +38,16 @@ enum {
 };
 
 enum {
-  ATA_REG_DATA       = 0x0,
-  ATA_REG_ERROR      = 0x1,
-  ATA_REG_FEAT       = 0x1,
-  ATA_REG_COUNT_LOW  = 0x2,
-  ATA_REG_LBA0       = 0x3,
-  ATA_REG_LBA1       = 0x4,
-  ATA_REG_LBA2       = 0x5,
-  ATA_REG_SELECT     = 0x6,
-  ATA_REG_CMD        = 0x7,
-  ATA_REG_STATUS     = 0x7,
-  ATA_REG_COUNT_HIGH = 0x8,
-  ATA_REG_LBA3       = 0x9,
-  ATA_REG_LBA4       = 0xa,
-  ATA_REG_LBA5       = 0xb,
-  ATA_REG_CONTROL    = 0xc,
-  ATA_REG_ALT_STATUS = 0xc,
-  ATA_REG_ADDR       = 0xd
+  ATA_REG_DATA   = 0x0,
+  ATA_REG_ERROR  = 0x1,
+  ATA_REG_FEAT   = 0x1,
+  ATA_REG_COUNT  = 0x2,
+  ATA_REG_LBA0   = 0x3,
+  ATA_REG_LBA1   = 0x4,
+  ATA_REG_LBA2   = 0x5,
+  ATA_REG_SELECT = 0x6,
+  ATA_REG_CMD    = 0x7,
+  ATA_REG_STATUS = 0x7,
 };
 
 enum {
@@ -71,5 +64,12 @@ enum {
 };
 
 enum {
-  ATA_CONTROL_NO_IRQS = 0x02
+  ATA_CONTROL_NO_IRQS = 0x02,
+};
+
+enum {
+  PATA_TYPE_ID   = 0x0000,
+  SATA_TYPE_ID   = 0xc33c,
+  PATAPI_TYPE_ID = 0xeb14,
+  SATAPI_TYPE_ID = 0x9669
 };
\ No newline at end of file
diff --git a/src/kernel/drive.c b/src/kernel/drive.c
index bf27ec6..b001aca 100644
--- a/src/kernel/drive.c
+++ b/src/kernel/drive.c
@@ -1,24 +1,24 @@
 #include "drive.h"
-#include "fat.h"
 #include "panic.h"
+#include "fat.h"
 
 uint8_t n_drives = 0;
 struct drive drives[256];
 
-drive_file_id_t unknown_get_file(struct drive *d, char *path) {
+__attribute__ ((const)) drive_file_id_t unknown_get_file(const struct drive *d, const char *path) {
   return 0;
 }
 
-void unknown_free_file(struct drive *d, drive_file_id_t fid) {
+void unknown_free_file(const struct drive *d, drive_file_id_t fid) {
   panic("Free file called on unknown file system");
 }
 
-void unknown_load_sector(struct drive *d, drive_file_id_t fid, uint32_t sector, void *at) {
+void unknown_load_sector(const struct drive *d, drive_file_id_t fid, uint32_t sector, void *at) {
   panic("Load sector called on unknown file system");
 }
 
-uint32_t unknown_get_free_sectors(struct drive *d) {
-  return d->n_sectors;
+__attribute__ ((const)) uint32_t unknown_get_free_sectors(const struct drive *d) {
+  return -1;
 }
 
 void determine_fs(struct drive *d) {
diff --git a/src/kernel/drive.h b/src/kernel/drive.h
index 8d3f3b2..ca6d1ee 100644
--- a/src/kernel/drive.h
+++ b/src/kernel/drive.h
@@ -14,15 +14,15 @@ struct drive {
   char *drive_type;
   char *fs_type;
 
-  uint8_t (*read_sectors)(struct drive *d, uint32_t start, uint32_t count, void *buffer);
-  uint8_t (*write_sectors)(struct drive *d, uint32_t start, uint32_t count, void *buffer);
+  uint8_t (*read_sectors)(const struct drive *d, uint32_t start, uint32_t count, void *buffer);
+  uint8_t (*write_sectors)(const struct drive *d, uint32_t start, uint32_t count, const void *buffer);
   uint32_t n_sectors;
   drive_id_t drive_id;
 
-  drive_file_id_t (*get_file)(struct drive *d, char *path);
-  void (*free_file)(struct drive *d, drive_file_id_t fid);
-  void (*load_sector)(struct drive *d, drive_file_id_t fid, uint32_t sector, void *at);
-  uint32_t (*get_free_sectors)(struct drive *d);
+  drive_file_id_t (*get_file)(const struct drive *d, const char *path);
+  void (*free_file)(const struct drive *d, drive_file_id_t fid);
+  void (*load_sector)(const struct drive *d, drive_file_id_t fid, uint32_t sector, void *at);
+  uint32_t (*get_free_sectors)(const struct drive *d);
   fs_id_t fs_id;
 };
 
diff --git a/src/kernel/fat.c b/src/kernel/fat.c
index 087d79e..807af00 100644
--- a/src/kernel/fat.c
+++ b/src/kernel/fat.c
@@ -1,9 +1,9 @@
-#include "fat.h"
-#include "ata.h"
-#include "panic.h"
 #include "drive.h"
-#include "mem.h"
+#include "panic.h"
 #include "util.h"
+#include "ata.h"
+#include "fat.h"
+#include "mem.h"
 
 #define MAX_FAT_DRIVES 16
 #define MAX_OPEN_FILES_PER_DRIVE 32
@@ -57,20 +57,19 @@ struct fat_info {
   uint8_t  fs_type[8];
 } __attribute__ ((packed));
 
-#define CTOS(c, fi) ((fi)->reserved_sectors + (fi)->sectors_per_fat * (fi)->fats + ((fi)->root_entries >> 4) + (c) - 2)
+#define CTOS(c, fdi) ((fdi)->data_start + (c) - 2)
 
 struct fat_drive_info {
-  struct fat_info *fi;
+  const struct fat_info *fi;
   uint16_t *fat;
+  uint16_t root_start;
+  uint16_t data_start;
   struct directory_entry open_files[MAX_OPEN_FILES_PER_DRIVE];
 };
 
 struct fat_drive_info infos[MAX_FAT_DRIVES];
 uint8_t next_id = 0;
 
-#define FI(n) ((struct fat_info *)(infos[n].fi + 3))
-#define FN(n, f) (infos[n].open_files[f - 1])
-
 uint8_t fat_driver_buffer[512];
 struct fat_info *next_fi;
 
@@ -80,8 +79,9 @@ void alloc_next_fi() {
       panic("Out of memory in FAT driver.");
 }
 
-struct drive *cur_drive;
+const struct drive *cur_drive;
 fs_id_t cur_id;
+const struct fat_drive_info *cur_fdi;
 struct directory_entry *cur_dir;
 
 //loads cluster `c`
@@ -91,7 +91,7 @@ void load_cluster(uint16_t c, void *to) {
     return;
   }
 
-  uint32_t s = CTOS(c, FI(cur_id));
+  uint32_t s = CTOS(c, cur_fdi);
   cur_drive->read_sectors(cur_drive, s, 1, to);
 }
 
@@ -99,7 +99,7 @@ uint16_t next_cluster(uint16_t c) {
   panic("TODO: compute next sector (or 0 for none)");
 }
 
-static inline bool check_fat_names(uint8_t *a, uint8_t *b) {
+static inline bool check_fat_names(const uint8_t *a, const uint8_t *b) {
   return (((uint32_t *)a)[0] == ((uint32_t *)b)[0]) &&
          (((uint32_t *)a)[1] == ((uint32_t *)b)[1]) &&
          (((uint16_t *)a)[8] == ((uint16_t *)b)[8]) &&
@@ -107,8 +107,8 @@ static inline bool check_fat_names(uint8_t *a, uint8_t *b) {
 }
 
 //after: cur_dir -> specified entry in root
-bool try_locate_root_entry(uint8_t *fat_name) {
-  uint32_t cur_dir_sect = FI(cur_id)->reserved_sectors + FI(cur_id)->sectors_per_fat * FI(cur_id)->fats - 1;
+bool try_locate_root_entry(const uint8_t *fat_name) {
+  uint32_t cur_dir_sect = cur_fdi->root_start - 1;
   cur_dir = (struct directory_entry *)(fat_driver_buffer + 512);
   while (true) {
     if (cur_dir == (struct directory_entry *)(fat_driver_buffer + 512)) {
@@ -127,7 +127,7 @@ bool try_locate_root_entry(uint8_t *fat_name) {
 
 //before: cur_dir -> entry of dir to search
 //after: cur_dir -> specified entry in dir
-bool try_locate_entry(uint8_t *fat_name) {
+bool try_locate_entry(const uint8_t *fat_name) {
   uint16_t cur_dir_cluster = cur_dir->first_cluster;
   load_cluster(cur_dir_cluster, fat_driver_buffer);
   cur_dir = (struct directory_entry *)fat_driver_buffer;
@@ -146,32 +146,41 @@ bool try_locate_entry(uint8_t *fat_name) {
   }
 }
 
-drive_file_id_t fat_get_file(struct drive *d, char *path) {
+drive_file_id_t fat_get_file(const struct drive *d, const char *path) {
   cur_drive = d;
   cur_id = d->drive_id;
+  cur_fdi = &infos[cur_id];
+  const struct directory_entry *open_files = cur_fdi->open_files - 1;
   for (drive_file_id_t n = 1; n != MAX_OPEN_FILES_PER_DRIVE + 1; ++n)
-    if (!*(uint8_t *)(&FN(d->drive_id, n))) {
-      panic("TODO: open path at FN(id, n)");
+    if (!*(uint8_t *)(&open_files[n])) {
+      panic("TODO: open path into open_files[n]");
       return n;
     }
   panic("Maximum number of files open reached for FAT drive.");
 }
 
-void fat_free_file(struct drive *d, drive_file_id_t fid) {
-  *(uint8_t *)(&FN(d->drive_id, fid)) = 0;
+void fat_free_file(const struct drive *d, drive_file_id_t fid) {
+  *(uint8_t *)(&infos[d->drive_id].open_files[fid - 1]) = 0;
 }
 
-void fat_load_sector(struct drive *d, drive_file_id_t fid, uint32_t sector, void *at) {
+void fat_load_sector(const struct drive *d, drive_file_id_t fid, uint32_t sector, void *at) {
   cur_drive = d;
   cur_id = d->drive_id;
-  uint16_t c = FN(d->drive_id, fid).first_cluster;
+  cur_fdi = &infos[cur_id];
+  uint16_t c = cur_fdi->open_files[fid - 1].first_cluster;
   for (uint32_t i = 0; i < sector; ++i)
     c = next_cluster(c);
   load_cluster(c, at);
 }
 
-uint32_t fat_get_free_sectors(struct drive *d) {
-  panic("TODO: get free sectors of drive");
+__attribute__ ((pure)) uint32_t fat_get_free_sectors(const struct drive *d) {
+  uint16_t *start = infos[d->fs_id].fat + 2;
+  uint16_t *end = start + d->n_sectors - infos[d->fs_id].data_start;
+  uint32_t count = 0;
+  for (uint16_t *i = start; i < end; ++i)
+    if (!*i)
+      ++count;
+  return count;
 }
 
 void init_fat() {
@@ -186,8 +195,8 @@ bool try_fat_init_drive(struct drive *d) {
     return false;
   memcpy(next_fi, fat_driver_buffer + 3, sizeof(struct fat_info));
   uint32_t *fs_type_32 = (uint32_t *)next_fi->fs_type;
-  if ((fs_type_32[0] != ('F' + 'A' * 256 + 'T' + 65536 + '1' * 16777216)) ||
-      (fs_type_32[1] != ('6' + ' ' * 256 + ' ' + 65536 + ' ' * 16777216)))
+  if ((fs_type_32[0] != ('F' + 'A' * 256 + 'T' * 65536 + '1' * 16777216)) ||
+      (fs_type_32[1] != ('6' + ' ' * 256 + ' ' * 65536 + ' ' * 16777216)))
     return false;
 
   d->fs_type = "FAT16";
@@ -199,10 +208,15 @@ bool try_fat_init_drive(struct drive *d) {
   d->fs_id = next_id;
   infos[next_id].fi = next_fi;
   infos[next_id].fat = allocate_pages(((next_fi->sectors_per_fat - 1) >> 3) + 1);
-  for (drive_file_id_t i = 0; i < MAX_OPEN_FILES_PER_DRIVE; ++i)
-    *(uint8_t *)&FN(next_id, i) = 0;
+  infos[next_id].root_start = next_fi->reserved_sectors + 
+                              next_fi->sectors_per_fat * next_fi->fats;
+  infos[next_id].data_start = infos[next_id].root_start +
+                              ((next_fi->root_entries - 1) >> 4) + 1;
 
   d->read_sectors(d, next_fi->reserved_sectors, next_fi->sectors_per_fat, infos[next_id].fat);
+  struct directory_entry *open_files = infos[next_id].open_files - 1;
+  for (drive_file_id_t i = 0; i < MAX_OPEN_FILES_PER_DRIVE; ++i)
+    *(uint8_t *)&open_files[i] = 0;
 
   alloc_next_fi();
   ++next_id;
diff --git a/src/kernel/fat.h b/src/kernel/fat.h
index d9db906..cadb073 100644
--- a/src/kernel/fat.h
+++ b/src/kernel/fat.h
@@ -1,8 +1,8 @@
 #ifndef FAT_H
 #define FAT_H
 
-#include <stdint.h>
 #include <stdbool.h>
+#include <stdint.h>
 #include "drive.h"
 
 void init_fat();
diff --git a/src/kernel/ide.c b/src/kernel/ide.c
index a2d3895..a32f149 100644
--- a/src/kernel/ide.c
+++ b/src/kernel/ide.c
@@ -1,171 +1,192 @@
-#include <stdint.h>
 #include <stdbool.h>
+#include <stdint.h>
+#include "drive.h"
 #include "panic.h"
 #include "util.h"
-#include "drive.h"
-#include "pci.h"
 #include "ata.h"
+#include "pci.h"
 
 #define MAX_IDE_DRIVES 8
 
 struct ide_drive_info {
   uint16_t base_port;
-  uint16_t control_port;
+  uint16_t alt_port;
   bool slave;
 };
 
 struct ide_drive_info ide_drives[MAX_IDE_DRIVES];
 drive_id_t n_ide_drives = 0;
 
-void spin_delay() {
-  for (uint32_t i = -1; i; --i)
-    ;
-}
-
-//return true on error condition
-bool poll(struct ide_drive_info *info) {
-  spin_delay();
-
-  uint8_t status;
+typedef uint16_t spinner_t;
 
-  while ((status = inb(info->base_port | ATA_REG_STATUS)) & ATA_STATUS_BUSY)
-    ;
+//returns the status after waiting
+uint8_t wait_after_cmd(uint16_t base_port) {
+  for (spinner_t n = -1; n; --n) {
+    uint8_t s = inb(base_port | ATA_REG_STATUS);
+    if (s & ATA_STATUS_ERROR)
+      panic("Error status in IDE driver.");
+    if (!(s & ATA_STATUS_BUSY))
+      return s;
+  }
+  panic("Spun out in IDE driver.");
+}
 
-  return (status & (ATA_STATUS_ERROR | ATA_STATUS_DRIVE_FAULT)) || !(status & ATA_STATUS_DRIVE_READY);
+//returns the status after waiting
+uint8_t wait_for_ready(uint16_t base_port) {
+  for (spinner_t n = -1; n; --n) {
+    uint8_t s = inb(base_port | ATA_REG_STATUS);
+    if (s & ATA_STATUS_ERROR)
+      panic("Error status in IDE driver.");
+    if (s & ATA_STATUS_DRIVE_READY)
+      return s;
+  }
+  panic("Spun out in IDE driver.");
 }
 
-uint8_t ide_ata_rs(struct drive *d, uint32_t start, uint32_t count, void *buffer) {
-  if (start & 0xf0000000)
-    panic("IDE ATA driver only supports LBA28 addressing currently.");
+//returns the status after waiting
+uint8_t wait_for_error_or_ready(uint16_t base_port) {
+  for (spinner_t n = -1; n; --n) {
+    uint8_t s = inb(base_port | ATA_REG_STATUS);
+    if (s & (ATA_STATUS_DRIVE_READY | ATA_STATUS_ERROR))
+      return s;
+  }
+  panic("Spun out in IDE driver.");
+}
 
-  struct ide_drive_info *info = ide_drives + d->drive_id;
+//returns the status after waiting
+uint8_t wait_for_data_ready_not_busy(uint16_t base_port) {
+  for (spinner_t n = -1; n; --n) {
+    uint8_t s = inb(base_port | ATA_REG_STATUS);
+    if (!(s & ATA_STATUS_BUSY) && (s & ATA_STATUS_DATA_READY))
+      return s;
+    if (s & ATA_STATUS_ERROR)
+      panic("Error status in IDE driver.");
+  }
+  panic("Spun out in IDE driver.");
+}
 
+uint8_t ide_ata_rs(const struct drive *d, uint32_t start, uint32_t count, void *buffer) {
+  if (start >= d->n_sectors)
+    return 0;
   if (start + count > d->n_sectors)
     count = d->n_sectors - start;
+  if (!count)
+    return 0;
 
+  if (start & 0xf0000000)
+    panic("IDE ATA driver does not support reads starting past 256MiB currently.");
   if (count & 0xffffff00)
-    panic("IDE ATA driver only supports reading up to 128k at a time currently.");
+    panic("IDE ATA driver does not support reads over 128kiB in length currently.");
 
   uint32_t lba = start & 0x00ffffff;
 
-  uint32_t spin = -1;
-  while (inb(info->base_port | ATA_REG_STATUS) & ATA_STATUS_BUSY)
-    if (!spin--)
-      panic("Spun out in IDE ATA reading");
+  struct ide_drive_info *info = ide_drives + d->drive_id;
 
   outb(info->base_port | ATA_REG_SELECT, (info->slave ? 0xf0 : 0xe0) | (start >> 24));
-  outb(info->base_port | ATA_REG_COUNT_LOW, count);
+  //spin?
+
+  outb(info->base_port | ATA_REG_COUNT, count);
   outb(info->base_port | ATA_REG_LBA0, lba);
   outb(info->base_port | ATA_REG_LBA1, lba >> 8);
   outb(info->base_port | ATA_REG_LBA2, lba >> 16);
 
-  uint16_t *buffer_16 = buffer;
+  outb(info->base_port | ATA_REG_CMD, ATA_CMD_READ);
+
+  uint16_t *buf16 = (uint16_t *)buffer;
 
   for (uint16_t i = 0; i < count; ++i) {
-    if (poll(info))
-      return i;
+    wait_for_data_ready_not_busy(info->base_port);
     for (uint16_t j = 0; j < 256; ++j)
-      *buffer_16++ = inw(info->base_port + ATA_REG_DATA);
+      *buf16++ = inw(info->base_port | ATA_REG_DATA);
   }
 
   return count;
 }
 
-uint8_t ide_ata_ws(struct drive *d, uint32_t start, uint32_t count, void *buffer) {
+uint8_t ide_ata_ws(const struct drive *d, uint32_t start, uint32_t count, const void *buffer) {
   panic("IDE ATA writing not implemented yet");
   return 0;
 }
 
-uint8_t ide_atapi_rs(struct drive *d, uint32_t start, uint32_t count, void *buffer) {
+uint8_t ide_atapi_rs(const struct drive *d, uint32_t start, uint32_t count, void *buffer) {
   //panic("IDE ATAPI reading not implemented yet");
   return 0;
 }
 
-uint8_t ide_atapi_ws(struct drive *d, uint32_t start, uint32_t count, void *buffer) {
+uint8_t ide_atapi_ws(const struct drive *d, uint32_t start, uint32_t count, const void *buffer) {
   panic("IDE ATAPI writing not implemented yet");
   return 0;
 }
 
 struct id_space {
-  uint16_t device_type;//0
-  uint8_t skip1[98 - 2];
-  uint16_t capabilities;//98
-  uint8_t skip2[120 - (98 + 2)];
+  uint8_t skip1[120];
   uint32_t max_lba;//120
-  uint8_t skip3[164 - (120 + 4)];
-  uint32_t command_sets;//164
-  uint8_t skip4[200 - (164 + 4)];
-  uint32_t max_lba_ext;//200
-  uint8_t skip5[512 - (200 + 4)];
-} __attribute__ ((__packed__));
-
-void read_id_space(uint16_t base_port, struct id_space *to) {
-  uint32_t *to_32 = (uint32_t *)to;
-  for (uint8_t i = 0; i < 128; ++i)
-    *(to_32++) = ind(base_port | ATA_REG_DATA);
-}
+  uint8_t skip2[512 - (120 + 4)];
+} __attribute__ ((__packed__ ));
 
-void test_drive(uint16_t base_port, uint16_t control_port, bool slave) {
-  outb(base_port | ATA_REG_SELECT, slave ? ATA_SLAVE_SELECT : ATA_MASTER_SELECT);
-  spin_delay();
+void vga_printsz(char *s);
 
-  outb(base_port | ATA_REG_CMD, ATA_CMD_ID);
-  spin_delay();
+void test_drive(uint16_t base_port, uint16_t alt_port, bool slave) {
+  if (n_ide_drives == MAX_IDE_DRIVES)
+    panic("Maximum number of IDE drives reached.");
 
-  if (!inb(base_port | ATA_REG_STATUS))
-    return;
+  struct ide_drive_info *next = ide_drives + n_ide_drives;
+  struct drive next_d;
+  next_d.drive_id = n_ide_drives;
 
-  if (n_ide_drives == MAX_IDE_DRIVES)
-    panic("Maximum IDE drives reached");
+  next->base_port = base_port;
+  next->alt_port = alt_port;
+  next->slave = slave;
 
-  outb(base_port | ATA_REG_CONTROL, ATA_CONTROL_NO_IRQS);
+  outb(base_port | ATA_REG_SELECT, slave ? 0xb0 : 0xa0);
+  outb(base_port | ATA_REG_COUNT, 0);
+  outb(base_port | ATA_REG_LBA0, 0);
+  outb(base_port | ATA_REG_LBA1, 0);
+  outb(base_port | ATA_REG_LBA2, 0);
 
-  struct ide_drive_info *this_drive = ide_drives + n_ide_drives;
-  this_drive->base_port = base_port;
-  this_drive->control_port = control_port;
-  this_drive->slave = slave;
+  outb(base_port | ATA_REG_CMD, ATA_CMD_ID);
 
-  struct drive data;
-  data.drive_id = n_ide_drives;
+  if (!inb(base_port | ATA_REG_STATUS))
+    return;
 
-  uint32_t spin_out = -1;
-  while (1) {//wait for identify to complete
-    uint8_t status = inb(base_port | ATA_REG_STATUS);
-    if (status & ATA_STATUS_ERROR) {
-      uint16_t type = inb(base_port | ATA_REG_LBA1) +
-                     (inb(base_port | ATA_REG_LBA2) << 8);
+  struct id_space ids;
 
-      //These two are listed on OSDev Wiki
-      //  as being ATAPI device types.
-      if ((type != 0xeb14) && (type != 0x9669))
-        return;
+  if (!(wait_for_error_or_ready(base_port) & ATA_STATUS_ERROR)) {
+    wait_for_ready(base_port);
+    for (uint16_t *ids_16 = (uint16_t *)&ids; ids_16 < (uint16_t *)&ids + 256; ++ids_16)
+      *ids_16 = inw(base_port | ATA_REG_DATA);
 
-      outb(base_port | ATA_REG_CMD, ATAPI_CMD_ID);
+    next_d.drive_type = "IDE PATA";
+    next_d.read_sectors = &ide_ata_rs;
+    next_d.write_sectors = &ide_ata_ws;
+  }
+  else {
+    uint16_t code = inb(base_port | 0x4) + (inb(base_port | 0x5) << 8);
+    if (!code) {
+      panic("PATA identification aborted.");
+    }
+    if (code == 0xeb14) {
+      next_d.drive_type = "IDE PATAPI";
+      next_d.read_sectors = &ide_atapi_rs;
+      next_d.write_sectors = &ide_atapi_ws;
 
-      data.read_sectors = &ide_atapi_rs;
-      data.write_sectors = &ide_atapi_ws;
-      data.drive_type = "IDE ATAPI";
-      break;
+      //TODO: issue proper identify command
+      ids.max_lba = -1;
     }
-    if (!(status & ATA_STATUS_BUSY) && (status & ATA_STATUS_DATA_READY)) {
-      data.read_sectors = &ide_ata_rs;
-      data.write_sectors = &ide_ata_ws;
-      data.drive_type = "IDE ATA";
-      break;
+    else if (code == 0xc33c) {
+      next_d.drive_type = "IDE SATA";
+      
+      //TODO: set up drive hooks, issue proper identify command
+      return;
     }
-    if (!spin_out--)
-      panic("IDE ATA identify won't complete");
   }
 
-  struct id_space id;
-  read_id_space(base_port, &id);
-
-  if (!(id.capabilities & ATA_CAP_LBA))
-    //TODO: CHS compability driver?
-    return;
-  data.n_sectors = (id.command_sets & ATA_SET_EXT) ? id.max_lba_ext : id.max_lba;
+  //in the future, maybe add support for 48-bit LBA, and/or CHS addressing
+  if (!ids.max_lba)
+    panic("Encountered ATA drive that doesn't support 28-bit LBA");
+  next_d.n_sectors = ids.max_lba;
 
-  commit_drive(data);
+  commit_drive(next_d);
   ++n_ide_drives;
 }
 
@@ -176,14 +197,9 @@ void init_ide() {
   while ((device = find_pci_device_from_class_and_subclass(PCI_MASS_STORAGE, PCI_IDE, check_from, &check_from))) {
     ++check_from;
 
-    uint16_t primary_base_port      = device->bar0 <= 1 ? 0x01f0 : device->bar0;
-    uint16_t primary_control_port   = device->bar1 <= 1 ? 0x03f6 : device->bar1;
-    uint16_t secondary_base_port    = device->bar2 <= 1 ? 0x0170 : device->bar2;
-    uint16_t secondary_control_port = device->bar3 <= 1 ? 0x0376 : device->bar3;
-
-    test_drive(primary_base_port,   primary_control_port,   false);
-    test_drive(primary_base_port,   primary_control_port,   true);
-    test_drive(secondary_base_port, secondary_control_port, false);
-    test_drive(secondary_base_port, secondary_control_port, true);
+    test_drive(0x01f0, 0x03f6, false);
+    test_drive(0x01f0, 0x03f6, true);
+    test_drive(0x0170, 0x0376, false);
+    test_drive(0x0170, 0x0376, true);
   }
 }
\ No newline at end of file
diff --git a/src/kernel/ide.h b/src/kernel/ide.h
index 44b02ec..47bcc49 100644
--- a/src/kernel/ide.h
+++ b/src/kernel/ide.h
@@ -1,12 +1,6 @@
 #ifndef IDE_H
 #define IDE_H
 
-#include <stdint.h>
-#include "drive.h"
-
 void init_ide();
 
-uint8_t ide_read_sectors(drive_id_t id, uint32_t start, uint32_t count, void *buffer);
-uint8_t ide_write_sectors(drive_id_t id, uint32_t start, uint32_t count, void *buffer);
-
 #endif
\ No newline at end of file
diff --git a/src/kernel/main.c b/src/kernel/main.c
index e5c0013..cbdebfa 100644
--- a/src/kernel/main.c
+++ b/src/kernel/main.c
@@ -1,30 +1,20 @@
 #include <stdint.h>
-#include "vga.h"
-#include "fat.h"
-#include "ide.h"
-#include "panic.h"
 #include "serial.h"
+#include "panic.h"
+#include "boot.h"
 #include "util.h"
+#include "vesa.h"
+#include "fat.h"
+#include "ide.h"
 #include "mem.h"
 #include "pci.h"
-#include "boot.h"
-#include "vesa.h"
-
-char nbuf[11];
-
-#define SOTL(field) field = (void *)((*((uint16_t *)(&field) + 1) << 16) + *(uint16_t *)(&field));
+#include "vga.h"
 
 __attribute__ ((noreturn)) void main() {
-  SOTL(VESA_INFO->oem)
-  SOTL(VESA_INFO->modes)
-  SOTL(VESA_INFO->vendor)
-  SOTL(VESA_INFO->pname)
-  SOTL(VESA_INFO->prev)
+  char nbuf[11];
 
   init_mmap();
-
   init_vesa();
-
   init_serial();
 
   vga_blank();
@@ -64,8 +54,10 @@ __attribute__ ((noreturn)) void main() {
   vga_printch('\n');
 
   init_fat();
+  //other fs drivers
 
   init_ide();
+  //other drive drivers
 
   u8_dec(n_drives, nbuf);
   vga_printsz(nbuf);
@@ -79,24 +71,27 @@ __attribute__ ((noreturn)) void main() {
     vga_printsz(nbuf);
     vga_printsz(" (");
     vga_printsz(d->drive_type);
-    vga_printsz("): ");
-
-    vga_printsz(d->fs_type);
     vga_printsz(", ");
 
     u32_dec(d->n_sectors / 2, nbuf);
     vga_printsz(nbuf);
     if (d->n_sectors % 2)
       vga_printsz(".5");
-    vga_printsz("k, ");
+    vga_printsz("k): ");
 
-    uint32_t free_sectors = d->get_free_sectors(d);
+    vga_printsz(d->fs_type);
 
-    u32_dec(free_sectors / 2, nbuf);
-    vga_printsz(nbuf);
-    if (d->n_sectors % 2)
-      vga_printsz(".5");
-    vga_printsz("k free.\n");
+    uint32_t free_sectors = d->get_free_sectors(d);
+    if (free_sectors != -1) {
+      u32_dec(free_sectors / 2, nbuf);
+      vga_printsz(", ");
+      vga_printsz(nbuf);
+      if (free_sectors % 2)
+        vga_printsz(".5");
+      vga_printsz("k free");
+    }
+
+    vga_printsz(".\n");
   }
 
   vga_printch('\n');
diff --git a/src/kernel/mem.c b/src/kernel/mem.c
index 2e8173d..d3baad3 100644
--- a/src/kernel/mem.c
+++ b/src/kernel/mem.c
@@ -1,6 +1,6 @@
 #include <stdint.h>
-#include <stdbool.h>
 #include "panic.h"
+#include "mem.h"
 
 #define DYNAMIC_START (0x10000000)
 #define DYNAMIC_END   (DYNAMIC_START + 65536 * 4096)
@@ -55,7 +55,7 @@ void *allocate_pages(uint16_t n) {
 }
 
 //in the future, change this to go by bytes or dwords instead of bits.
-void free_pages(void *ptr, uint16_t n) {
+void free_pages(const void *ptr, uint16_t n) {
   uint16_t page = ADDR_TO_PAGE(ptr);
   for (uint32_t i = page; i < page + n; ++i)
     CLEAR_PAGE(i);
diff --git a/src/kernel/mem.h b/src/kernel/mem.h
index 913f70b..9a9ae79 100644
--- a/src/kernel/mem.h
+++ b/src/kernel/mem.h
@@ -7,7 +7,7 @@ extern uint16_t pages_left;
 
 void init_mmap();
 
-void *allocate_pages(uint16_t n);
-void free_pages(void *ptr, uint16_t n);
+void *allocate_pages(uint16_t n) __attribute__ ((malloc));
+void free_pages(const void *ptr, uint16_t n);
 
 #endif
\ No newline at end of file
diff --git a/src/kernel/panic.c b/src/kernel/panic.c
index 93944ff..e04ae38 100644
--- a/src/kernel/panic.c
+++ b/src/kernel/panic.c
@@ -1,10 +1,7 @@
-#include <stdint.h>
-#include "vga.h"
-#include "serial.h"
-#include "util.h"
 #include "panic.h"
+#include "vga.h"
 
-void panic(char *message) {
+void panic(const char *message) {
   vga_set_color(0x4f);
   vga_blank();
   vga_printsz("Kernel panic: ");
diff --git a/src/kernel/panic.h b/src/kernel/panic.h
index 7d2e9df..08328f2 100644
--- a/src/kernel/panic.h
+++ b/src/kernel/panic.h
@@ -1,8 +1,6 @@
 #ifndef PANIC_H
 #define PANIC_H
 
-#include <stdint.h>
-
-void panic(char *message) __attribute__ ((noreturn));
+void panic(const char *message) __attribute__ ((noreturn));
 
 #endif
\ No newline at end of file
diff --git a/src/kernel/pci.c b/src/kernel/pci.c
index fe96c4c..5d8170d 100644
--- a/src/kernel/pci.c
+++ b/src/kernel/pci.c
@@ -1,8 +1,8 @@
+#include "panic.h"
 #include "boot.h"
-#include "mem.h"
 #include "util.h"
+#include "mem.h"
 #include "pci.h"
-#include "panic.h"
 
 enum {
   PCP_SELECT = 0x0cf8,
@@ -59,11 +59,6 @@ void pci_device_check(uint16_t number) {
   next_device->class = class >> 24;
   next_device->subclass = class >> 16;
   next_device->iface = class >> 8;
-
-  next_device->bar0 = pci_read_config(number, 4);
-  next_device->bar1 = pci_read_config(number, 5);
-  next_device->bar2 = pci_read_config(number, 6);
-  next_device->bar3 = pci_read_config(number, 7);
 }
 
 void pci_init() {
diff --git a/src/kernel/pci.h b/src/kernel/pci.h
index 1ab5936..8ff9f45 100644
--- a/src/kernel/pci.h
+++ b/src/kernel/pci.h
@@ -20,16 +20,10 @@ struct pci_device {
   uint8_t class;
   uint8_t subclass;
   uint8_t iface;
-
-  uint32_t bar0;
-  uint32_t bar1;
-  uint32_t bar2;
-  uint32_t bar3;
-  //etc
 };
 
 extern uint16_t n_pci_devices;
-struct pci_device *nth_pci_device(uint16_t n);
+struct pci_device *nth_pci_device(uint16_t n) __attribute__ ((pure));
 
 struct pci_device *find_pci_device_from_class_and_subclass(uint8_t class, uint8_t subclass, uint16_t start, uint16_t *index);
 
diff --git a/src/kernel/plef.c b/src/kernel/plef.c
index 2cba843..710943f 100644
--- a/src/kernel/plef.c
+++ b/src/kernel/plef.c
@@ -1,13 +1,12 @@
 #include <stdint.h>
-#include <stdbool.h>
-#include "plef.h"
 #include "drive.h"
-#include "util.h"
+#include "plef.h"
 #include "task.h"
+#include "util.h"
 
 #define PLEF_MAGIC 0xb9ba4c50
 
-task_handle plef_run(struct drive *d, char *path) {
+task_handle plef_run(const struct drive *d, const char *path) {
   drive_file_id_t h = d->get_file(d, path);
   if (!h)
     return 0;
diff --git a/src/kernel/plef.h b/src/kernel/plef.h
index 29100ee..a14ea9b 100644
--- a/src/kernel/plef.h
+++ b/src/kernel/plef.h
@@ -2,7 +2,6 @@
 #define PLEF_H
 
 #include <stdint.h>
-#include <stdbool.h>
 #include "drive.h"
 
 typedef uint8_t task_handle;
@@ -17,6 +16,6 @@ struct plef_header {
   uint32_t entry_point;
 } __attribute__ ((packed));
 
-task_handle plef_run(struct drive *d, char *path);
+task_handle plef_run(const struct drive *d, const char *path);
 
 #endif
\ No newline at end of file
diff --git a/src/kernel/serial.c b/src/kernel/serial.c
index 0f7abe6..c92f173 100644
--- a/src/kernel/serial.c
+++ b/src/kernel/serial.c
@@ -1,5 +1,6 @@
-#include <stdint.h>
 #include <stdbool.h>
+#include <stdint.h>
+#include "serial.h"
 #include "util.h"
 
 enum {
@@ -76,12 +77,12 @@ void sout(char b) {
   outb(CP_1 | CP_DATA, (uint8_t)b);
 }
 
-void soutsz(char *s) {
+void soutsz(const char *s) {
   while (*s)
     sout(*(s++));
 }
 
-void soutsn(char *s, uint8_t n) {
+void soutsn(const char *s, uint8_t n) {
   while (n--)
     sout(*(s++));
 }
diff --git a/src/kernel/serial.h b/src/kernel/serial.h
index bb12edb..2fb21a6 100644
--- a/src/kernel/serial.h
+++ b/src/kernel/serial.h
@@ -1,14 +1,14 @@
 #ifndef SERIAL_H
 #define SERIAL_H
 
-#include <stdint.h>
 #include <stdbool.h>
+#include <stdint.h>
 
-bool serr();
+bool serr() __attribute__ ((pure));
 void init_serial();
 void sout(char b);
-void soutsz(char *s);
-void soutsn(char *s, uint8_t n);
+void soutsz(const char *s);
+void soutsn(const char *s, uint8_t n);
 char sin();
 void sinsn(char *s, uint8_t n);
 
diff --git a/src/kernel/task.c b/src/kernel/task.c
index c08a195..3e64639 100644
--- a/src/kernel/task.c
+++ b/src/kernel/task.c
@@ -1,5 +1,5 @@
-#include "task.h"
 #include "panic.h"
+#include "task.h"
 
 segment_id new_segment(bool is_code, uint32_t length, uint32_t *location_out) {
   panic("TODO: make new segment");
diff --git a/src/kernel/task.h b/src/kernel/task.h
index add668b..c3f2acd 100644
--- a/src/kernel/task.h
+++ b/src/kernel/task.h
@@ -1,8 +1,8 @@
 #ifndef TASK_H
 #define TASK_H
 
-#include <stdint.h>
 #include <stdbool.h>
+#include <stdint.h>
 
 typedef uint8_t segment_id;
 typedef uint8_t task_handle;
diff --git a/src/kernel/util.c b/src/kernel/util.c
index 1531f83..29d7e3f 100644
--- a/src/kernel/util.c
+++ b/src/kernel/util.c
@@ -1,10 +1,10 @@
-#include <stdint.h>
-#include "panic.h"
 #include <stdbool.h>
+#include <stdint.h>
 #include "drive.h"
 
-void memcpy(void *to, void *from, uint32_t n) {
-  uint32_t *tp = to, *fp = from;
+void memcpy(void *to, const void *from, uint32_t n) {
+  uint32_t *tp = to;
+  const uint32_t *fp = from;
   while (n >= 4) {
     *(tp++) = *(fp++);
     n -= 4;
@@ -14,7 +14,7 @@ void memcpy(void *to, void *from, uint32_t n) {
     *(tpp++) = *(fpp++);
 }
 
-void fmcpy(void *to, struct drive *d, drive_file_id_t f, uint32_t from, uint32_t n) {
+void fmcpy(void *to, const struct drive *d, drive_file_id_t f, uint32_t from, uint32_t n) {
   uint8_t buf[512];
   d->load_sector(d, f, from >> 9, buf);
   uint16_t from_low = from & 511;
diff --git a/src/kernel/util.h b/src/kernel/util.h
index 243541c..324f379 100644
--- a/src/kernel/util.h
+++ b/src/kernel/util.h
@@ -10,8 +10,8 @@ static inline void outb(uint16_t port, uint8_t value) {
   : : "a"(value), "Nd"(port));
 }
 static inline uint8_t inb(uint16_t port) {
-  uint8_t value;
-  asm volatile (
+  volatile uint8_t value;
+  asm (
     "inb %1, %0"
   : "=a"(value) : "Nd"(port));
   return value;
@@ -22,8 +22,8 @@ static inline void outw(uint16_t port, uint16_t value) {
   : : "a"(value), "Nd"(port));
 }
 static inline uint16_t inw(uint16_t port) {
-  uint16_t value;
-  asm volatile (
+  volatile uint16_t value;
+  asm (
     "inw %1, %0"
   : "=a"(value) : "Nd"(port));
   return value;
@@ -34,15 +34,15 @@ static inline void outd(uint16_t port, uint32_t value) {
   : : "a"(value), "Nd"(port));
 }
 static inline uint32_t ind(uint16_t port) {
-  uint32_t value;
-  asm volatile (
+  volatile uint32_t value;
+  asm (
     "inl %1, %0"
   : "=a"(value) : "Nd"(port));
   return value;
 }
 
-void memcpy(void *to, void *from, uint32_t n);
-void fmcpy(void *to, struct drive *d, drive_file_id_t f, uint32_t from, uint32_t n);
+void memcpy(void *to, const void *from, uint32_t n);
+void fmcpy(void *to, const struct drive *d, drive_file_id_t f, uint32_t from, uint32_t n);
 
 void u32_dec(uint32_t n, char *b);
 void u16_dec(uint16_t n, char *b);
diff --git a/src/kernel/vesa.c b/src/kernel/vesa.c
index e781249..4cdabb2 100644
--- a/src/kernel/vesa.c
+++ b/src/kernel/vesa.c
@@ -1,5 +1,21 @@
 #include "vesa.h"
 
+uint16_t screen_width;
+uint16_t screen_height;
+uint8_t bpp;
+
+void *frame_buffer;
+
+void put_pixel(uint16_t x, uint16_t y, color c) {
+
+}
+
+void screen_fill(color c) {
+
+}
+
 void init_vesa() {
-  
+//  for (void *v = 0; v < 0x65536; ++v) {
+//    if (*(uint32_t *)v == 'P' + 'M' * 256 + 'I' * 65536 + 'D' * 16777216)
+//  }
 }
\ No newline at end of file
diff --git a/src/kernel/vesa.h b/src/kernel/vesa.h
index 495b593..b2f17c8 100644
--- a/src/kernel/vesa.h
+++ b/src/kernel/vesa.h
@@ -1,23 +1,16 @@
 #ifndef VESA_H
 #define VESA_H
 
-struct video_mode {
-  //TODO
-};
+#include <stdint.h>
 
-#define VESA_INFO \
-  ((struct { \
-    uint32_t sig; \
-    uint16_t vbe_ver; \
-    char *oem; \
-    uint32_t capabilities; \
-    struct video_mode *modes; \
-    uint16_t vram_size_high; \
-    uint16_t soft_ver; \
-    char *vendor; \
-    char *pname; \
-    char *prev; \
-  } *)0x4200)
+extern uint16_t screen_width;
+extern uint16_t screen_height;
+extern uint8_t bpp;
+
+typedef uint32_t color;
+
+void put_pixel(uint16_t x, uint16_t y, color c);
+void screen_fill(color c);
 
 void init_vesa();
 
diff --git a/src/kernel/vga.c b/src/kernel/vga.c
index 788ce6c..e103732 100644
--- a/src/kernel/vga.c
+++ b/src/kernel/vga.c
@@ -1,5 +1,5 @@
-#include <stdint.h>
 #include <stdbool.h>
+#include <stdint.h>
 
 #define VGA_COM_MIRROR
 
@@ -50,12 +50,12 @@ void vga_printch(char ch) {
     vga_scroll();
 }
 
-void vga_printsz(char *sz) {
+void vga_printsz(const char *sz) {
   while (*sz)
     vga_printch(*(sz++));
 }
 
-void vga_printsn(char *sn, uint8_t n) {
+void vga_printsn(const char *sn, uint8_t n) {
   while (n--)
     vga_printch(*(sn++));
 }
\ No newline at end of file
diff --git a/src/kernel/vga.h b/src/kernel/vga.h
index 1be2131..e88ddfe 100644
--- a/src/kernel/vga.h
+++ b/src/kernel/vga.h
@@ -7,7 +7,7 @@ void vga_set_color(uint8_t color);
 void vga_blank();
 void vga_scroll();
 void vga_printch(char ch);
-void vga_printsz(char *sz);
-void vga_printsn(char *sn, uint8_t n);
+void vga_printsz(const char *sz);
+void vga_printsn(const char *sn, uint8_t n);
 
 #endif
\ No newline at end of file