linux-kernel - Re: [RFC] Creating an eeprom class

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Message-ID: <CAAXf6LXGOzqu=VeSdeuu3kNBjVBcobp-2keDmSZ_JSL-72Uu+Q@mail.gmail.com>
Date:	Mon, 21 Jan 2013 08:25:59 +0100
From:	Thomas De Schampheleire <patrickdepinguin@...il.com>
To:	Greg KH <gregkh@...uxfoundation.org>
Cc:	linux-kernel@...r.kernel.org, Wolfram Sang <w.sang@...gutronix.de>,
	Anatolij Gustschin <agust@...x.de>,
	Frodo Looijaard <frodol@....nl>,
	Philip Edelbrock <phil@...roedge.com>,
	Ben Gardner <bgardner@...tec.com>,
	Ronny Meeus <Ronny.Meeus@...il.com>
Subject: Re: [RFC] Creating an eeprom class

On Sun, Jan 20, 2013 at 11:39 PM, Greg KH <gregkh@...uxfoundation.org> wrote:
> On Sun, Jan 20, 2013 at 07:08:28PM +0100, Thomas De Schampheleire wrote:
>> [plaintext and fixed address of David Brownell]
>
> David passed away a year or so ago, so that's really not going to help :(

So sorry to hear that, I was not aware...

>
>> Hi,
>>
>> Several of the eeprom drivers that live in drivers/misc/eeprom export
>> a binary sysfs file 'eeprom'. If a userspace program or script wants
>> to access this file, it needs to know the full path, for example:
>>
>> /sys/bus/spi/devices/spi32766.0/eeprom
>>
>> The problem with this approach is that it requires knowledge about the
>> hardware configuration: is the eeprom on the SPI bus, the I2C bus, or
>> maybe memory mapped?
>>
>> It would therefore be more interesting to have a bus-agnostic way to
>> access this eeprom file, for example:
>> /sys/class/eeprom/eeprom0/eeprom
>>
>> Maybe it'd be even better to use a more generic class name than
>> 'eeprom', since there are several types of eeprom-like devices that
>> you could export this way.
>
> Does all of the existing "eeprom" devices use the same userspace
> interface?  If so, yes, having a "class" would make sense.

All but one do. That one (eeprom_93cx6.c) exports its read/write
functions to other kernel code, and is used in several
wireless/ethernet drivers.

>
>> Or should we rather hook the eeprom code into the mtd subsystem?
>
> Why mtd?

Because an eeprom is a piece of memory. Maybe mtd is overkill in term
of the operations supported, but from a high-level perspective an
eeprom is a memory technology device, right?

Thanks,
Thomas
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