Accessing EEPROM from Linux driver

Accessing EEPROM from Linux driver

[Yegor Yefremov]

I've an external i2c attached EEPROM, where I hold the MAC addresses
for 3 interfaces including WLAN. My SoC is am3517 from TI. I found
EEPROM driver under drivers/misc/eeprom/at24.c I can access EEPROM via
sysfs from userland. What were the appropriate method of accessing
EEPROM from a network driver? AFAIK no functions were exported from
eeprom.c.

Regards,
Yegor

Re: Accessing EEPROM from Linux driver

[Bill Gatliff]

Yegor:

On Tue, Jan 24, 2012 at 10:51 AM, Yegor Yefremov
<yegorslists-gM/Ye1E23mwN+BqQ9rBEUg@public.gmane.org> wrote:
> What were the appropriate method of accessing
> EEPROM from a network driver? AFAIK no functions were exported from
> eeprom.c.

You probably want to read those values in userspace, and then stuff
them back into the ethernet device via ifconfig or similar when you
bring the interface up.  Then you can leave both drivers as-is.


b.g.
-- 
Bill Gatliff
bgat-uPd5UNENI//N9NzbbXoYwQ@public.gmane.org

Re: Accessing EEPROM from Linux driver

[Wolfram Sang]

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> sysfs from userland. What were the appropriate method of accessing
> EEPROM from a network driver? AFAIK no functions were exported from
> eeprom.c.

Please state always which version you are using. There is code exactly
for your use case in the driver since ~2.6.30 (and clearly described as
such).

437 /*
438  * This lets other kernel code access the eeprom data. For example, it
439  * might hold a board's Ethernet address, or board-specific calibration
440  * data generated on the manufacturing floor.
441  */

Regards,

    Wolfram

-- 
Pengutronix e.K.                           | Wolfram Sang                |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |

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Re: Accessing EEPROM from Linux driver

[Yegor Yefremov]

On Tue, Jan 24, 2012 at 11:06 AM, Wolfram Sang <w.sang-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org> wrote:
>
>> sysfs from userland. What were the appropriate method of accessing
>> EEPROM from a network driver? AFAIK no functions were exported from
>> eeprom.c.
>
> Please state always which version you are using. There is code exactly
> for your use case in the driver since ~2.6.30 (and clearly described as
> such).
>
> 437 /*
> 438  * This lets other kernel code access the eeprom data. For example, it
> 439  * might hold a board's Ethernet address, or board-specific calibration
> 440  * data generated on the manufacturing floor.
> 441  */

Thanks. My bad, I overlooked this.

Regards,
Yegor

Re: Accessing EEPROM from Linux driver

[Yegor Yefremov]

On Tue, Jan 24, 2012 at 11:13 AM, Yegor Yefremov
<yegorslists-gM/Ye1E23mwN+BqQ9rBEUg@public.gmane.org> wrote:
> On Tue, Jan 24, 2012 at 11:06 AM, Wolfram Sang <w.sang-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org> wrote:
>>
>>> sysfs from userland. What were the appropriate method of accessing
>>> EEPROM from a network driver? AFAIK no functions were exported from
>>> eeprom.c.
>>
>> Please state always which version you are using. There is code exactly
>> for your use case in the driver since ~2.6.30 (and clearly described as
>> such).
>>
>> 437 /*
>> 438  * This lets other kernel code access the eeprom data. For example, it
>> 439  * might hold a board's Ethernet address, or board-specific calibration
>> 440  * data generated on the manufacturing floor.
>> 441  */
>
> Thanks. My bad, I overlooked this.

Wolfram, do you have any example how to access at24_macc_read()? My
kernel is 2.6.37. Theres is a statement to export this code to the
kernel via chip.setup(), which appears to be NULL. What headers do I
need in the network driver?

Regards,
Yegor

Re: Accessing EEPROM from Linux driver

[Wolfram Sang]

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> Wolfram, do you have any example how to access at24_macc_read()? My
> kernel is 2.6.37. Theres is a statement to export this code to the
> kernel via chip.setup(), which appears to be NULL. What headers do I
> need in the network driver?

I haven't used it myself, but using LXR [1] you can check current users
of at24_platform_data and find users (davinci) using this feature.

[1] http://lxr.linux.no/#linux+v3.2.1/include/linux/i2c/at24.h

-- 
Pengutronix e.K.                           | Wolfram Sang                |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |

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Re: Accessing EEPROM from Linux driver

[Yegor Yefremov]

On Tue, Jan 24, 2012 at 12:13 PM, Wolfram Sang <w.sang-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org> wrote:
>> Wolfram, do you have any example how to access at24_macc_read()? My
>> kernel is 2.6.37. Theres is a statement to export this code to the
>> kernel via chip.setup(), which appears to be NULL. What headers do I
>> need in the network driver?
>
> I haven't used it myself, but using LXR [1] you can check current users
> of at24_platform_data and find users (davinci) using this feature.
>
> [1] http://lxr.linux.no/#linux+v3.2.1/include/linux/i2c/at24.h

Thanks. It's working now. I was lucky to have DaVinci based EMAC in
am3517, so I only had to adjust the code on the platform side. The
driver itself was left untouched. For USB based NIC and WLAN I'll need
to get my hands on their drivers :-(

I submitted a patch to eeprom's documentation. At this point I have a
question? Are those TODO items still valid? At least in regards of
write capability? In 2.6.37 kernel I can write to EEPROM through sysfs
entry. Unfortunately I can't test any 3.x kernel because PSP for
am3517 is still not finished.

Regards,
Yegor

Re: Accessing EEPROM from Linux driver

[samir]

Yegor Yefremov <yegorslists@...> writes:

Dear all,
I interest about at24_macc_read, but I don't how to call the function,
Could you give me some example, 
thanks and regards.