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.
> .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?
>
> 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.
---
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
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