Messages in this thread Patch in this message | | | Date | Fri, 7 Nov 2003 09:38:36 -0500 (EST) | From | Mauricio Martinez <> | Subject | [PATCH] 2.4.22 drivers/cdrom/cdu31a.c |
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This patch fixes a problem (multiple reads of the same data) while reading from a CDU31 SONY CD-ROM drive.
The hack was originally suggested by Corey Minyard a few months ago (and working well for months in my old P5/200), but for some reason it didn't appear in the current stable release of the kernel - Patch submitted just for the sake of code cleanliness.
-Mauricio Martinez mauricio@coe.neu.edu --- drivers/cdrom/cdu31a.c.orig Fri Jun 13 09:51:32 2003 +++ drivers/cdrom/cdu31a.c Wed Oct 29 23:03:10 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, @@ -1361,12 +1361,10 @@ res_reg[0] = 0; res_reg[1] = 0; *res_size = 0; - /* Make sure that bytesleft doesn't exceed the buffer size */ - if (nblocks > 4) nblocks = 4; 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; @@ -1535,7 +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. @@ -1548,6 +1546,7 @@ unsigned int res_size; int num_retries; unsigned long flags; + char *buffer; #if DEBUG @@ -1618,6 +1617,7 @@ block = CURRENT->sector; nblock = CURRENT->nr_sectors; + buffer = CURRENT->buffer; if (!sony_toc_read) { printk("CDU31A: TOC not read\n"); @@ -1697,8 +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); @@ -1717,6 +1726,10 @@ block, nblock); } goto try_read_again; +/* } else if (nblock > 0) { + printk("Number of blocks left: %d\n", nblock); + end_request(1); +*/ } else { end_request(1); }
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