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SubjectRe: [PATCH] 2.4.20 drivers/cdrom/cdu31a.c
I don't guess anyone I've sent documentation to has taken up support of 
this drive. It's amazing that any of these things are still running,
since I think they stop manufacturing them in 1994. I don't think I
have a machine that it will even work in any more. I guess they were
well-built drives.

The change you are suggesting is probably not the best, you probably
need to fix it higher up to do multiple requests if nsect is > 4. I've
attached a patch. It compiles, but I obviously can't test it.

Looking through the code, there's obvious SMP problems and a few other
things. I have a new machine with an ISA slot (I think), I might try to
plug it in.

-Corey

Mauricio Martinez wrote:

>This patch fixes the kernel oops while trying to read a data CD. Thanks to
>Brian Gerst and Faik Uygur for your suggestions.
>
>It looks like the variable nblocks must be <= 4 so the read ahead buffer
>size is not exceeded (which is the cause of the oops). Changing its value
>doesn't seem to be the right way, but it makes the device work properly.
>
>Feedback of any sort welcome.
>
>
>
--- drivers/cdrom/cdu31a.c.old Fri Feb 7 09:16:08 2003
+++ drivers/cdrom/cdu31a.c Fri Feb 7 09:42:53 2003
@@ -1341,7 +1341,7 @@
#endif
}

-/* read data from the drive. Note the nsect must be <= 4. */
+/* read data from the drive. Note the nblocks must be <= 4. */
static void
read_data_block(char *buffer,
unsigned int block,
@@ -1364,7 +1364,7 @@
bytesleft = nblocks * 512;
offset = 0;

- /* If the data in the read-ahead does not match the block offset,
+ /* If the data in the read ahead does not match the block offset,
then fix things up. */
if (((block % 4) * 512) != ((2048 - readahead_dataleft) % 2048)) {
sony_next_block += block % 4;
@@ -1384,9 +1384,9 @@
readahead_buffer + (2048 -
readahead_dataleft),
readahead_dataleft);
- readahead_dataleft = 0;
bytesleft -= readahead_dataleft;
offset += readahead_dataleft;
+ readahead_dataleft = 0;
} else {
/* The readahead will fill the whole buffer, get the data
and return. */
@@ -1533,7 +1533,7 @@

/*
* The OS calls this to perform a read or write operation to the drive.
- * Write obviously fail. Reads to a read ahead of sony_buffer_size
+ * Writes obviously fail. Reads to a read ahead of sony_buffer_size
* bytes to help speed operations. This especially helps since the OS
* uses 1024 byte blocks and the drive uses 2048 byte blocks. Since most
* data access on a CD is done sequentially, this saves a lot of operations.
@@ -1546,6 +1546,7 @@
unsigned int res_size;
int num_retries;
unsigned long flags;
+ char *buffer;


#if DEBUG
@@ -1616,6 +1617,7 @@

block = CURRENT->sector;
nblock = CURRENT->nr_sectors;
+ buffer = CURRENT->buffer;

if (!sony_toc_read) {
printk("CDU31A: TOC not read\n");
@@ -1695,8 +1697,17 @@
}
}

- read_data_block(CURRENT->buffer, block, nblock,
- res_reg, &res_size);
+ if (nblock >= 4) {
+ read_data_block(buffer, block, 4,
+ res_reg, &res_size);
+ nblock -= 4;
+ block += 4;
+ buffer += 4 * 512;
+ } else {
+ read_data_block(buffer, block, nblock,
+ res_reg, &res_size);
+ nblock = 0;
+ }
if (res_reg[0] == 0x20) {
if (num_retries > MAX_CDU31A_RETRIES) {
end_request(0);
@@ -1714,6 +1725,8 @@
translate_error(res_reg[1]),
block, nblock);
}
+ goto try_read_again;
+ } else if (nblock > 0) {
goto try_read_again;
} else {
end_request(1);
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