From: Bartosz Golaszewski <bgolaszewski@baylibre.com>
To: Wolfram Sang <wsa@the-dreams.de>
Cc: linux-i2c <linux-i2c@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [RESEND PATCH v2 0/9] eeprom: at24: at24cs series serial number read
Date: Mon, 4 Jan 2016 15:01:54 +0100 [thread overview]
Message-ID: <CAMpxmJWmgk+9oJXZnRFRzidLaasoMyuDuZmVWWrs6dwNM=+k6Q@mail.gmail.com> (raw)
In-Reply-To: <20160102205041.GC1589@katana>
2016-01-02 21:50 GMT+01:00 Wolfram Sang <wsa@the-dreams.de>:
> On Fri, Dec 11, 2015 at 02:55:10PM +0100, Bartosz Golaszewski wrote:
>> 2015-12-11 13:08 GMT+01:00 Wolfram Sang <wsa@the-dreams.de>:
>> > On Wed, Dec 02, 2015 at 11:25:17AM +0100, Bartosz Golaszewski wrote:
>> >> Chips from the at24cs EEPROM series have an additional read-only memory area
>> >> containing a factory pre-programmed serial number. In order to access it, a
>> >> dummy write must be executed before reading the serial number bytes.
>> >
>> > Can't you instantiate a read-only EEPROM on this second address? Or a
>> > seperate driver attaching to this address? What is the advantage of
>> > having this in at24?
>> >
>>
>> The regular memory area and serial number read-only block share the
>> internal address pointer. We must ensure that there's no race
>> conditions between normal EEPROM reads/writes and serial number reads.
>
> I don't get it. Both, regular at24 reads and the serial read, setup the
> pointer every time by using two messages, first write to set the
> pointer, then read. The per-adapter lock makes sure those two messages
> will not get interrupted.
If that's correct, then is there any need to have an additional mutex
for at24_data?
> So, it looks to me that it would be OK if a
> serial read access gets inbetween a eeprom read access. Am I wrong?
>
In that case would the preferred method be to access the regular
memory area like before - by allocating, for example, a 24c02 device -
while allocating a second device - in that case 24cs02 - on the
corresponding serial number address would give the user access to the
serial number via the eeprom sysfs attribute (which for the latter
would be read-only and 16 bytes in size)?
Best regards,
Bartosz Golaszewski
next prev parent reply other threads:[~2016-01-04 14:01 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-12-02 10:25 [RESEND PATCH v2 0/9] eeprom: at24: at24cs series serial number read Bartosz Golaszewski
2015-12-02 10:25 ` [RESEND PATCH v2 1/9] eeprom: at24: platform_data: use BIT() macro Bartosz Golaszewski
2015-12-02 10:25 ` [RESEND PATCH v2 2/9] eeprom: at24: new flag in platform_data Bartosz Golaszewski
2015-12-02 10:25 ` [RESEND PATCH v2 3/9] eeprom: at24: tie up an additional address for at24cs series Bartosz Golaszewski
2015-12-02 10:25 ` [RESEND PATCH v2 4/9] eeprom: at24: support reading of the serial number Bartosz Golaszewski
2015-12-02 10:25 ` [RESEND PATCH v2 5/9] eeprom: at24: export the serial number through sysfs Bartosz Golaszewski
2015-12-02 10:25 ` [RESEND PATCH v2 6/9] eeprom: at24: improve the device_id table readability Bartosz Golaszewski
2015-12-02 10:25 ` [RESEND PATCH v2 7/9] eeprom: at24: add the at24cs series to the list of supported devices Bartosz Golaszewski
2015-12-02 10:25 ` [RESEND PATCH v2 8/9] eeprom: at24: remove a reduntant if Bartosz Golaszewski
2015-12-02 10:25 ` [RESEND PATCH v2 9/9] eeprom: at24: readability tweaks Bartosz Golaszewski
2015-12-11 12:08 ` [RESEND PATCH v2 0/9] eeprom: at24: at24cs series serial number read Wolfram Sang
2015-12-11 13:55 ` Bartosz Golaszewski
2015-12-21 14:29 ` Bartosz Golaszewski
2016-01-02 20:50 ` Wolfram Sang
2016-01-04 14:01 ` Bartosz Golaszewski [this message]
2016-01-05 18:58 ` Wolfram Sang
2016-01-07 16:10 ` Bartosz Golaszewski
2016-01-09 21:09 ` Wolfram Sang
2016-01-11 13:57 ` Bartosz Golaszewski
-- strict thread matches above, loose matches on Subject: below --
2015-11-24 9:44 Bartosz Golaszewski
2015-11-17 9:52 Bartosz Golaszewski
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