Why eeprom driver is read-only ?

From: valdis.kletnieks@vt.edu (valdis.kletnieks at vt.edu)
To: kernelnewbies@lists.kernelnewbies.org
Subject: Why eeprom driver is read-only ?
Date: Mon, 19 Nov 2018 17:32:03 -0500	[thread overview]
Message-ID: <177621.1542666723@turing-police.cc.vt.edu> (raw)
In-Reply-To: <CAJ2oMhLXRqM6xR_FXD6ckX5D3m7iz2oeSd8B2qvZj8ka+oHMSA@mail.gmail.com>

On Tue, 20 Nov 2018 00:04:03 +0200, Ranran said:

> That's interesting...
> I think the name is confusing, because this chips are also writable.
>
> Not only this, but in arm the eeprom (at24) is writable!
> But in the x86 I am using, it is readonly in kernel code:
> https://android.googlesource.com/kernel/omap/+/glass-omap-xrr02/drivers/misc/eeprom/eeprom.c
> static struct bin_attribute eeprom_attr = {
> .attr = {
> .name = "eeprom",
> .mode = S_IRUGO,
> },
> .size = EEPROM_SIZE,
> .read = eeprom_read,
> };

Well, at least in the mainline kernel, we have this at the top of the eeprom.c file:

/* Addresses to scan */
static const unsigned short normal_i2c[] = { 0x50, 0x51, 0x52, 0x53, 0x54,
                                        0x55, 0x56, 0x57, I2C_CLIENT_END };

/* Size of EEPROM in bytes */
#define EEPROM_SIZE             256

which is pretty obviously intended for "very small eeprom hanging off an I2C adapter",
and thus probably *NOT* the boot ROM that the BIOS lives in.
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