linux-kernel - Re: [PATCH] eeprom: at24: Add support for large EEPROMs connected to SMBus adapters

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Date:	Fri, 27 Mar 2015 14:01:08 +0100
From:	Wolfram Sang <wsa@...-dreams.de>
To:	Guenter Roeck <linux@...ck-us.net>
Cc:	linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] eeprom: at24: Add support for large EEPROMs connected to
 SMBus adapters

On Fri, Mar 27, 2015 at 05:51:11AM -0700, Guenter Roeck wrote:
> On 03/27/2015 01:09 AM, Wolfram Sang wrote:
> >
> >>just to give you an update: I do have some code, but it is a bit messy,
> >>and it doesn't work well for ds2482 (the chip behind it still hangs up
> >>if I access it in parallel through i2c-dev). On top of that, it causes
> >>pretty significant slow-downs when accessing other devices on the same
> >>bus at the same time. Not surprising, I guess, since it expands the scope
> >>of the bus lock significantly.
> >
> >Just to get a better idea: Did you try taking the adapter_lock before
> >the two SMBus command which needed to be concatenated (and use
> >smbus_xfer directly)?
> >
> I did. I didn't use smbus_xfer directly, though, but introduced lockless
> versions of the various smbus commands, and kept using those.

And then the chip still hangs? Or was that the performance penalty here?


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