Why eeprom driver is read-only ?
Hello, What is the reason that kernel driver of eeprom is configured only as read-only ? Is it because the BIOS is stored there ? Is there a way to make it writable ? Thank you, Ran
On 11/19/18 7:08 AM, Ranran wrote:
Hello,
What is the reason that kernel driver of eeprom is configured only as read-only ?
Is it because the BIOS is stored there ?
Is there a way to make it writable ?
Thank you, Ran
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because the ROM is read only? -- So many immigrant groups have swept through our town that Brooklyn, like Atlantis, reaches mythological proportions in the mind of the world - RI Safir 1998 http://www.mrbrklyn.com DRM is THEFT - We are the STAKEHOLDERS - RI Safir 2002 http://www.nylxs.com - Leadership Development in Free Software http://www.brooklyn-living.com Being so tracked is for FARM ANIMALS and and extermination camps, but incompatible with living as a free human being. -RI Safir 2013
Hello, It seems that some drivers in drivers/misc/eeprom does support write access. For example at24.c seems to have a function at24_write(). https://github.com/torvalds/linux/blob/master/drivers/misc/eeprom/at24.c However some drivers doesn’t have write support, I believe it is because of simplicity - some eeprom are used for read only, such as ddr4 spd eeprom. Point me out if I am wrong. Chriz Enviado desde mi iPhone
El 19 nov 2018, a las 9:12 p. m., Ruben Safir <ruben@mrbrklyn.com> escribió:
On 11/19/18 7:08 AM, Ranran wrote: Hello,
What is the reason that kernel driver of eeprom is configured only as read-only ?
Is it because the BIOS is stored there ?
Is there a way to make it writable ?
Thank you, Ran
_______________________________________________ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
because the ROM is read only?
-- So many immigrant groups have swept through our town that Brooklyn, like Atlantis, reaches mythological proportions in the mind of the world - RI Safir 1998 http://www.mrbrklyn.com DRM is THEFT - We are the STAKEHOLDERS - RI Safir 2002
http://www.nylxs.com - Leadership Development in Free Software http://www.brooklyn-living.com
Being so tracked is for FARM ANIMALS and and extermination camps, but incompatible with living as a free human being. -RI Safir 2013
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On Mon, Nov 19, 2018 at 3:13 PM Ruben Safir <ruben@mrbrklyn.com> wrote:
On 11/19/18 7:08 AM, Ranran wrote:
Hello,
What is the reason that kernel driver of eeprom is configured only as read-only ?
Is it because the BIOS is stored there ?
Is there a way to make it writable ?
Thank you, Ran
_______________________________________________ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
because the ROM is read only?
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... static struct bin_attribute eeprom_attr = { .attr = { .name = "eeprom", .mode = S_IRUGO, }, .size = EEPROM_SIZE, .read = eeprom_read, }; Regards, ran
-- So many immigrant groups have swept through our town that Brooklyn, like Atlantis, reaches mythological proportions in the mind of the world - RI Safir 1998 http://www.mrbrklyn.com DRM is THEFT - We are the STAKEHOLDERS - RI Safir 2002
http://www.nylxs.com - Leadership Development in Free Software http://www.brooklyn-living.com
Being so tracked is for FARM ANIMALS and and extermination camps, but incompatible with living as a free human being. -RI Safir 2013
_______________________________________________ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
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... 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.
On Tue, Nov 20, 2018 at 12:32 AM <valdis.kletnieks@vt.edu> wrote:
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... 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.
although I think that in my system it is a flash rom which stores the BIOS, so I really don't know what's the use of the eeprom.... I need a very small amout of data (several bytes) to save some non volatile information in x86 system. I can't use disk for this, but can use any other peripheral or even x86 chip on board. Now it also seems that I can't use the eeprom becuase of the kernel limitation (can I open it for writing if the BIOS is not stored there??) I don't have any idea where I can find such storage. Does x86 include some programmable registers ? Do you have any idea where I can store the data ? Thanks
On Mon, 19 Nov 2018 14:08:26 +0200, Ranran said:
What is the reason that kernel driver of eeprom is configured only as read-only ?
Probably depends on the hardware. I'm pretty sure that *some* eeproms are writable.
Is it because the BIOS is stored there ?
Remember that the BIOS is stored in one of what may be several eeproms in the system - graphics cards and other controllers probably have their own eeproms. You might want to think about why most systems do a restart after updating the BIOS, and then ask yourself if you really want to write to it while the system is up....
Is there a way to make it writable ?
Depends on which eeprom you're talking about.
participants (4)
-
Chriz Chow -
Ranran -
Ruben Safir -
valdis.kletnieks＠vt.edu