Re: [RFC][WORTH IT?][PATCH] bcma: make use of crc8 lib

["Arend van Spriel" <arend@broadcom.com>]

On 06/15/2011 08:29 PM, Rafał Miłecki wrote:
> W dniu 15 czerwca 2011 14:09 użytkownik Arend van Spriel
> <arend@broadcom.com>  napisał:
>> On 06/15/2011 01:53 PM, Rafał Miłecki wrote:
>>>   static u8 bcma_sprom_crc(const u16 *sprom)
>>>   {
>>> -       int word;
>>> -       u8 crc = 0xFF;
>>> +       u8 crc;
>>> +       u8 sprom2[SSB_SPROMSIZE_WORDS_R4 * 2 - 1];
>>> +       u8 table[CRC8_TABLE_SIZE];
>>> +       u16 word;
>>>
>>> +       /* u16 to u8 */
>>>         for (word = 0; word<    SSB_SPROMSIZE_WORDS_R4 - 1; word++) {
>>> -               crc = bcma_crc8(crc, sprom[word]&    0x00FF);
>>> -               crc = bcma_crc8(crc, (sprom[word]&    0xFF00)>>    8);
>>> +               sprom2[word * 2] = sprom[word]&    0x00FF;
>>> +               sprom2[(word * 2) + 1] = (sprom[word]&    0xFF00)>>    8;
>>>         }
>>> -       crc = bcma_crc8(crc, sprom[SSB_SPROMSIZE_WORDS_R4 - 1]&    0x00FF);
>>> +       /* 127th byte */
>>> +       sprom2[(SSB_SPROMSIZE_WORDS_R4 * 2) - 2] =
>>> +                               sprom[SSB_SPROMSIZE_WORDS_R4 - 1]&
>>>   0x00FF;
>>> +
>>> +       /* Prepare table, 0xAB is x^8 + x^7 + x^6 + x^4 + x^2 + 1 */
>>> +       crc8_populate_lsb(table, 0xAB);
>>> +
>>> +       /* Calculate */
>>> +       crc = crc8(table, sprom2, (SSB_SPROMSIZE_WORDS_R4 * 2) - 1, 0xFF);
>>>         crc ^= 0xFF;
>>>
>>>         return crc;
>> You could do (I think):
>>
>> crc8_populate_lsb(table, 0xAB);
>> for (word = 0; word<    SSB_SPROMSIZE_WORDS_R4; word++) {
>>         u16 val = cpu_to_le16(sprom[word]);
>>         crc = crc8(table,&val, sizeof(u16), crc);
>> }
> Maybe not a perfect/optimal solution (crc8 focuses on tables, we do
> double loop instead) but should work. Thanks for the tip.

Agree. In brcm80211 we convert the entire sprom, calculate, and convert 
it back. Also not perfect I think as it loops over de sprom data twice.

Gr. AvS

-- 
Almost nobody dances sober, unless they happen to be insane.
-- H.P. Lovecraft --