Re: [PATCH 1/4] media: dvb/af9015, implement eeprom hashing

From: Antti Palosaari
Date: Sun Jan 24 2010 - 18:53:19 EST

On 01/24/2010 06:35 PM, Jiri Slaby wrote:
On 01/24/2010 05:16 PM, Antti Palosaari wrote:
+ af9015_config.eeprom_sum = 0;
+ for (reg = 0; reg< eeprom_size / sizeof(u32); reg++) {
+ af9015_config.eeprom_sum *= GOLDEN_RATIO_PRIME_32;
+ af9015_config.eeprom_sum += le32_to_cpu(((u32 *)eeprom)[reg]);
+ }
+ deb_info("%s: eeprom sum=%.8x\n", __func__,

Does this sum contain all 256 bytes from EEPROM? 256/4 is 64.

Yes it does. It is computed as a hashed sum of 32-bit numbers (4 bytes)
-- speed (does not matter) and larger space of hashes. Hence the
division by 4. The cast does the trick: ((u32 *)eeprom)[reg] -- reg
index is on a 4-byte basis.

OK, true. Anyhow, I don't know if this hashing formula is good enough - changing it later could be really pain. I compared it to the one used for em28xx driver and it was different. Could someone with better knowledge check that?

Generally it is good and ready for submission.

Acked-by: Antti Palosaari <crope@xxxxxx>

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