2011/6/23 Jean Delvare <[email protected]>:
> Hi Christian,
>
> On Tue, 21 Jun 2011 13:54:52 +0200, Christian Gmeiner wrote:
>> Hi community,
>>
>> I am working on an embedded x86 device, which has an at24 based
>> eeprom. I am using
>> the i2c_eg20t driver to access the i2c bus. To be able to access the
>> eeprom in a separated
>> driver I did this:
>>
>> /* technical description of our used EEPROM */
>> static struct at24_platform_data custom_i2c_eeprom_info = {
>> .byte_len = EEPROM_BYTE_LEN,
>> .page_size = 16,
>> .flags = 0,
>
> Note that you don't have to mention struct members with value 0 (or
> NULL), as this is the default.
>
Thanks for this hint.
>> .setup = content_read,
>> .context = NULL,
>> };
>>
>> /* EEPROM at24 */
>> static struct i2c_board_info __initdata i2c_info[] = {
>> {
>> I2C_BOARD_INFO("24c04", 0x50),
>> .platform_data = &custom_i2c_eeprom_info,
>> },
>> };
>>
>> In the init function of my custom driver I do this:
>>
>> /* register known devices on i2c bus */
>> status = i2c_register_board_info(0, i2c_info, ARRAY_SIZE(i2c_info))
>
> Out of curiosity, where did you put this code? Does x86 finally support
> per-machine initialization as e.g. arm does?
>
I have an other x86 based target machine, which runs a 2.6.36.4
kernel, where I created
a new driver under drivers/misc called custom_eeprom.c. The driver is
used to access
some special values stored in eeprom easily from userspace via /proc.
static int __init custom_eeprom_init(void)
{
...
/* register known devices on i2c bus */
status = i2c_register_board_info(0, i2c_info, ARRAY_SIZE(i2c_info));
/* create procfs entries */
...
return ret;
}
It is AMD LX800 based an I use the scx200_acb i2c driver, modified to
use i2c_add_numbered_adapter().
I did a small test with 3.0-rc4 on the LX800 target, but it get an
oops.. so there seems to be some changes in the involved subsystems.
>>
>> Now I run in some troubles... see
>> http://www.spinics.net/lists/linux-i2c/msg02022.html
>
> I see that I already replied to this post...
>
>> What options do I have to get this running? I could use
>> i2c_add_numbered_adapter, but I don't
>> want to touch too much from mainline kernel sources.
>
> It seems difficult to use i2c_add_numbered_adapter() unconditionally, as
> i2c-eg20t is a PCI driver so you don't get to pass platform data to it.
> Furthermore, i2c_add_numbered_adapter() is only suitable if machine
> setup code could be run before any device driver is initialized;
> otherwise odds are that another driver will have picked the i2c bus
> number you wanted. I am unsure if this is possible at all on x86 at the
> moment.
>
> The way I would do it is from i2c-eg20t itself. Take a look at i2c-i801
> for an example: at the end of the probe function, there is
> hardware-specific code to instantiate a few I2C devices. If you have a
> way to uniquely, reliably detect that you are running on your specific
> target system, you can do the same.
>
> I don't think it is particularly nice, BTW, but this is the only way I
> found so far with what the i2c subsystem core offers. If anyone has
> suggestions how to improve this, please speak up.
>
> If you want to be able to use i2c_add_numbered_adapter() conditionally
> without the help of platform data, then you need a hint from i2c-core.
> Would the following patch help you? If it does, and others show
> interest, and there are no objections, this could go upstream in kernel
> 3.1.
>
I get an oops quite early in kernel bootup... I will try to catch it
and if you are
interested I will post it here.
> ---
> drivers/i2c/busses/i2c-eg20t.c | 7 ++++++-
> drivers/i2c/i2c-boardinfo.c | 20 ++++++++++++++++++++
> include/linux/i2c.h | 5 +++++
> 3 files changed, 31 insertions(+), 1 deletion(-)
>
> --- linux-3.0-rc4.orig/drivers/i2c/i2c-boardinfo.c 2011-05-20
> 10:42:40.000000000 +0200
> +++ linux-3.0-rc4/drivers/i2c/i2c-boardinfo.c 2011-06-23 10:15:56.000000000
> +0200
> @@ -90,3 +90,23 @@ i2c_register_board_info(int busnum,
>
> return status;
> }
> +
> +/**
> + * i2c_adapter_is_static - let drivers know if their bus is static
> + * @busnum: identifies the bus
> + *
> + * After calling this function, i2c bus drivers can decide whether
> + * to call i2c_add_adapter or i2c_add_numbered_adapter.
> + */
> +int
> +i2c_adapter_is_static(int busnum)
> +{
> + int is_static;
> +
> + down_write(&__i2c_board_lock);
> + is_static = busnum < __i2c_first_dynamic_bus_num;
> + up_write(&__i2c_board_lock);
> +
> + return is_static;
> +}
> +EXPORT_SYMBOL_GPL(i2c_adapter_is_static);
> --- linux-3.0-rc4.orig/include/linux/i2c.h 2011-06-21 10:32:32.000000000
> +0200
> +++ linux-3.0-rc4/include/linux/i2c.h 2011-06-23 09:58:21.000000000 +0200
> @@ -306,6 +306,7 @@ extern void i2c_unregister_device(struct
> extern int
> i2c_register_board_info(int busnum, struct i2c_board_info const *info,
> unsigned n);
> +extern int i2c_adapter_is_static(int busnum);
> #else
> static inline int
> i2c_register_board_info(int busnum, struct i2c_board_info const *info,
> @@ -313,6 +314,10 @@ i2c_register_board_info(int busnum, stru
> {
> return 0;
> }
> +static inline int i2c_adapter_is_static(int busnum)
> +{
> + return 0;
> +}
> #endif /* I2C_BOARDINFO */
>
> /*
> --- linux-3.0-rc4.orig/drivers/i2c/busses/i2c-eg20t.c 2011-05-30
> 20:45:09.000000000 +0200
> +++ linux-3.0-rc4/drivers/i2c/busses/i2c-eg20t.c 2011-06-23
> 10:48:26.000000000 +0200
> @@ -787,7 +787,12 @@ static int __devinit pch_i2c_probe(struc
>
> pch_adap->dev.parent = &pdev->dev;
>
> - ret = i2c_add_adapter(pch_adap);
> + if (i2c_adapter_is_static(i)) {
> + /* We assume that a single PCI device is present */
> + pch_adap->nr = i;
> + ret = i2c_add_numbered_adapter(pch_adap);
> + } else
> + ret = i2c_add_adapter(pch_adap);
> if (ret) {
> pch_pci_err(pdev, "i2c_add_adapter[ch:%d] FAILED\n",
> i);
> goto err_i2c_add_adapter;
>
>
>
> --
> Jean Delvare
>
--
Christian Gmeiner, MSc
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