From: Jiri Slaby <jirislaby@gmail.com>
To: Antti Palosaari <crope@iki.fi>
Cc: Jiri Slaby <jslaby@suse.cz>,
linux-kernel@vger.kernel.org,
Mauro Carvalho Chehab <mchehab@redhat.com>,
linux-media@vger.kernel.org
Subject: Re: [PATCH 1/4] media: dvb/af9015, implement eeprom hashing
Date: Sun, 24 Jan 2010 17:35:04 +0100 [thread overview]
Message-ID: <4B5C76B8.4090700@gmail.com> (raw)
In-Reply-To: <4B5C7258.1010605@iki.fi>
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__,
>> af9015_config.eeprom_sum);
>
> 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.
regards,
--
js
next prev parent reply other threads:[~2010-01-24 16:35 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-01-13 20:00 [PATCH 1/1] media: dvb-usb/af9015, add IR support for digivox mini II Jiri Slaby
2010-01-14 19:09 ` Antti Palosaari
2010-01-22 15:10 ` [PATCH 1/4] media: dvb/af9015, implement eeprom hashing Jiri Slaby
2010-01-24 16:16 ` Antti Palosaari
2010-01-24 16:35 ` Jiri Slaby [this message]
2010-01-24 23:52 ` Antti Palosaari
2010-01-22 15:10 ` [PATCH 2/4] media: dvb/af9015, factor out remote setting Jiri Slaby
2010-01-24 23:53 ` Antti Palosaari
2010-01-22 15:10 ` [PATCH 3/4] media: dvb/af9015, refactor " Jiri Slaby
2010-01-24 23:54 ` Antti Palosaari
2010-01-22 15:10 ` [PATCH 4/4] media: dvb/af9015, add hashes support Jiri Slaby
2010-01-24 23:55 ` Antti Palosaari
2010-01-22 15:11 ` [PATCH 1/1] media: dvb-usb/af9015, add IR support for digivox mini II Jiri Slaby
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