linux-kernel - Re: [PATCH RFC] misc/at24: distinguish between eeprom and fram chips

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Message-ID: <20121205164153.GA5011@pengutronix.de>
Date:	Wed, 5 Dec 2012 17:41:53 +0100
From:	Wolfram Sang <w.sang@...gutronix.de>
To:	Lars Poeschel <poeschel@...onage.de>
Cc:	gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org,
	linux-i2c@...r.kernel.org
Subject: Re: [PATCH RFC] misc/at24: distinguish between eeprom and fram
 chips

Hi,

On Wed, Dec 05, 2012 at 10:43:07AM +0100, Lars Poeschel wrote:
> I see there where to much "no"s to get anything in, but thank you for
> your comments and explanations.

Not necessarily, just not in this form :)

> 
> > > I wanted to use a fm24c04 i2c fram chip with linux. I grepped the source
> > > and found nothing. I later found that my chip can be handled by at24
> > > eeprom driver. It creates a sysfs file called eeprom to read from and
> > > write to the chip. Userspace has no chance to distinguish if it is
> > > writing an eeprom or a fram chip.
> > 
> > Why should it?
> 
> Because writes are much faster and it doesn't have to take care on erase
> cycles. It could use other write strategies on such devices and update
> informations that have to survive power downs more often.

I agree. I think that a seperate attribute named e.g. 'page_size' would
be more helpful than renaming the binary file to fram?

> > The method of accessing EEPROMs is used by way more chips than FRAMs.
> > So, I'd prefer to have the text updated more generic like "EEPROMs and
> > similar devices like RAMs, ROMs, etc...". Describing setting .flags in
> > Kconfig is overkill.
> 
> A patch updating Kconfig is below.

Looks good from a glimpse, will apply it later.

> No one knows all chips out there.
> For the fm24c04 I use page_size != chip_size. It does not buffer but it has 
> two pages, 256 bytes each.

Yup, it uses two I2C adresses...

Thanks,

   Wolfram

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

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