1 files changed, 47 insertions, 22 deletions

diff --git a/kernel/fd.c b/kernel/fd.c
index 19068c4..f6563ea 100644
--- a/kernel/fd.c
+++ b/kernel/fd.c
@@ -28,6 +28,9 @@
 #define NTYPES (sizeof(ftypes) / sizeof(struct ftype))
 #define NFDS (sizeof(fd) / sizeof(struct fdrive))
 
+/* time (ms) to wait for the FDC to become ready (RQM set) */
+#define READ_TIMEOUT 2
+
 /* helper macros for converting LBA into CHS */
 #define C(lba, ft) \
   (lba / (ft->h * ft->s))
@@ -45,6 +48,9 @@
 /* TODO: seek before reading */
 /* TODO: check drive ready state in floppy driver (ensure the drive door is closed before any operation) */
 /* TODO: cut back on printk() usage */
+/* TODO: implement retries for operations likely to fail */
+/* TODO: eliminate potential context switches in read_sect() */
+/* TODO: test that a drive actually exists before beginning an operation */
 
 /* TODO: implement a timeout to prevent system hangs */
 #define WAITIRQ(x) ({ \
@@ -61,6 +67,15 @@ struct sense_result {
   uint8_t cyl;
 } __attribute__((packed));
 
+struct req {
+  uint16_t c;
+  uint8_t h;
+  uint8_t s;
+  struct task_struct *wait;
+  struct req *nread;
+  struct req *nseek;
+};
+
 struct ftype {
   uint16_t c;
   uint8_t h;
@@ -72,7 +87,6 @@ struct ftype {
 
 struct fdrive {
   struct ftype *type;
-  struct task_struct *seek_wait;
   uint8_t cyl;
   uint8_t st0;
 };
@@ -93,9 +107,10 @@ static struct fdrive fd[4];
 
 static char buffer[512] __attribute__((aligned (0x10000)));
 
-static struct task_struct *read_wait;
+static struct req *read_queue;
 
 static ssize_t read_data(void *buf, size_t len) {
+  long timeout;
   ssize_t c = 0;
   uint8_t *p = buf;
 
@@ -105,17 +120,12 @@ static ssize_t read_data(void *buf, size_t len) {
   if(len > SSIZE_MAX)
     len = SSIZE_MAX;
 
-  /*
-   * TODO: fix this.
-   * This entire routine really is garbage.
-   * It doesn't use a timeout (potentially
-   * hanging the entire system) and doesn't
-   * handle the DIO flag properly.
-   */
   while(len--) {
-    while(!(inb(FDMSR) & 0x80));
+    timeout = uptime() + READ_TIMEOUT;
+
+    while(!(inb(FDMSR) & 0x80) && uptime() < timeout);
 
-    if(!(inb(FDMSR) & 0x40))
+    if(!(inb(FDMSR) & 0xC0))
       break;
 
     *p++ = inb(FDDATA);
@@ -129,9 +139,7 @@ static ssize_t read_data(void *buf, size_t len) {
   while((inb(FDMSR) & 0xC0) == 0xC0)
     inb(FDDATA);
 
-  if(!c)
-    return -1;
-  return c;
+  return !c ? -1 : c;
 }
 
 static void write_data(void *buf, size_t len) {
@@ -237,7 +245,7 @@ static void reset(void) {
   while((inb(FDMSR) & wait));
 }
 
-int fd_read_sect(int sect) {
+int fd_read_sect(int sect, struct req *r) {
   ssize_t in;
   struct {
     uint8_t st0;
@@ -261,14 +269,30 @@ int fd_read_sect(int sect) {
     0xFF
   };
 
-  cli();
-  if(read_wait)
-    sleep_on(&read_wait);
-  sti();
+  /* prepare a read request */
+  memset(r, 0, sizeof(struct req));
+  r->c = C(sect, fd[0].type);
+  r->h = H(sect, fd[0].type);
+  r->s = S(sect, fd[0].type);
+
+  if(read_queue) {
+    r->nread = read_queue->nread;
+    read_queue->nread = r;
+    sleep_on(&r->wait);
+  } else {
+    read_queue = r;
+  }
 
   printk("[fd] Reading sector 0x%01x (C: 0x%01x, H: 0x%01x, S: 0x%01x)\n", sect, cmd[2], cmd[3], cmd[4]);
 
-  WAITIRQ(write_data(cmd, sizeof(cmd)));
+  cli();
+  write_data(cmd, sizeof(cmd));
+  sti();
+  sleep_on(&r->wait);
+
+  read_queue = r->nread;
+  if(read_queue)
+    wake_up(&read_queue->wait);
 
   in = read_data(&res, sizeof(res));
   if(in == sizeof(res) && !(res.st0 & 0xC0)) {
@@ -285,7 +309,8 @@ void fd_interrupt(void) {
   struct sense_result sr;
   irq_fired = 1;
 
-  wake_up(&read_wait);
+  if(read_queue)
+    wake_up(&read_queue->wait);
 
   if((inb(FDMSR) & 0xC0) != 0x80)
     return;
@@ -301,7 +326,7 @@ void fd_block_read(struct buffer *b) {
   void *p = b->b_data;
 
   for(i = SECTS(b->b_block); i < SECTS(b->b_block + 1); i++) {
-    if(fd_read_sect(i)) {
+    if(fd_read_sect(i, b->b_data)) {
       b->b_device = 0;
       return;
     }