[Stgt-devel] [PATCH] read block limits data offset one off

[Albert Pauw]

FUJITA Tomonori wrote:
> On Sat, 19 Jul 2008 19:34:54 +0200
> Albert Pauw <albert.pauw at gmail.com> wrote:
>
>   
>> According to SSC-2 Rev 8 the Read Block Limits return data is made up of 
>> 6 bytes, index 0-5:
>>
>> Byte 0 contains granularity (bits 0-4)
>> Byte 1-3 contain  Maximum Block Length Limit (MSB first)
>> Byte 4-5 contain Minimum Block Length Limit (MSB first)
>>
>> Since all bytes are zeroed first, Byte 1 is zero.
>>
>> I also added a defined value for the granularity, as defined by the
>> Read Block Limits command, and calculate the blk_len out of it.
>> Now you only need to change the GRANULARITY parameter.
>>
>> So the patch is:
>>
>> --- ssc.c    2008-07-19 19:29:58.000000000 +0200
>> +++ ssc.c.new    2008-07-19 19:30:54.000000000 +0200
>>     
>
> Thanks, few comments.
>
>   
>> @@ -35,6 +35,7 @@
>>  #include "tgtadm_error.h"
>>  
>>  #define BLK_SHIFT    9
>> +#define GRANULARITY    9
>>  
>>  
>>  static int ssc_rw(int host_no, struct scsi_cmd *cmd)
>> @@ -73,16 +74,16 @@
>>  {
>>      uint8_t *data;
>>      uint8_t buf[256];
>> -    uint16_t blk_len = 0x200;
>> +    uint16_t blk_len = 1 << GRANULARITY;
>>  
>>      memset(buf, 0, sizeof(buf));
>>      data = buf;
>>  
>> -    data[0] = 9;
>> +    data[0] = GRANULARITY;
>>     
>
> For the future changes, can we add:
>
> data[1] = (blk_len >> 16) & 0xff
>
>   
>>      data[2] = blk_len >> 8;
>>      data[3] = blk_len & 0x0ff;
>>     
>
> Let's do:
>
> data[2] = (blk_len >> 8) & 0xff;
> data[3] = blk_len & 0xff;
>
>   
>> -    data[5] = blk_len >> 8;
>> -    data[6] = blk_len & 0x0ff;
>> +    data[4] = blk_len >> 8;
>> +    data[5] = blk_len & 0x0ff;
>>     
>
> dito.
>   
Yes, it would catch blk_len > 65536 nicely.
>   
>>      memcpy(scsi_get_in_buffer(cmd), data, 6);
>>      eprintf("In ssc_read_block_limit \n");
>>     
>
> We should check the buffer length but it would be better to do that
> with a different patch.
>   

Still trying to grasp the code, since my programming skills are very dusty.
Next time I'll use git for a patch and sign it.

Cheers