[PATCH] i2c: slave-eeprom: Add an OF device ID table

[PATCH] i2c: slave-eeprom: Add an OF device ID table

[Javier Martinez Canillas]

The driver doesn't have a struct of_device_id table but supported devices
are registered via Device Trees as shown in the following DT binding doc:

Documentation/devicetree/bindings/i2c/i2c-designware.txt

But this works on the assumption that a I2C device registered via OF will
always match a legacy I2C device ID and that the MODALIAS reported will
always be of the form i2c:<device>.

And this could change in the future so the correct approach is to have an
OF device ID table if the devices are registered via OF.

Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>

---

 drivers/i2c/i2c-slave-eeprom.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/drivers/i2c/i2c-slave-eeprom.c b/drivers/i2c/i2c-slave-eeprom.c
index b2039f94c9d8..20226860cfe7 100644
--- a/drivers/i2c/i2c-slave-eeprom.c
+++ b/drivers/i2c/i2c-slave-eeprom.c
@@ -17,6 +17,7 @@
 #include <linux/i2c.h>
 #include <linux/init.h>
 #include <linux/module.h>
+#include <linux/of_device.h>
 #include <linux/of.h>
 #include <linux/slab.h>
 #include <linux/spinlock.h>
@@ -108,7 +109,12 @@ static int i2c_slave_eeprom_probe(struct i2c_client *client, const struct i2c_de
 {
 	struct eeprom_data *eeprom;
 	int ret;
-	unsigned size = id->driver_data;
+	unsigned size;
+
+	if (client->dev.of_node)
+		size = (kernel_ulong_t)of_device_get_match_data(&client->dev);
+	else
+		size = id->driver_data;
 
 	eeprom = devm_kzalloc(&client->dev, sizeof(struct eeprom_data) + size, GFP_KERNEL);
 	if (!eeprom)
@@ -154,9 +160,16 @@ static const struct i2c_device_id i2c_slave_eeprom_id[] = {
 };
 MODULE_DEVICE_TABLE(i2c, i2c_slave_eeprom_id);
 
+static const struct of_device_id i2c_slave_eeprom_of_match[] = {
+	{ .compatible = "linux,slave-24c02", .data = (void *)(2048 / 8) },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, i2c_slave_eeprom_of_match);
+
 static struct i2c_driver i2c_slave_eeprom_driver = {
 	.driver = {
 		.name = "i2c-slave-eeprom",
+		.of_match_table = i2c_slave_eeprom_of_match,
 	},
 	.probe = i2c_slave_eeprom_probe,
 	.remove = i2c_slave_eeprom_remove,
-- 
2.13.3

Re: [PATCH] i2c: slave-eeprom: Add an OF device ID table

[Wolfram Sang]

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On Wed, Aug 09, 2017 at 12:12:56PM +0200, Javier Martinez Canillas wrote:
> The driver doesn't have a struct of_device_id table but supported devices
> are registered via Device Trees as shown in the following DT binding doc:
> 
> Documentation/devicetree/bindings/i2c/i2c-designware.txt

Uhhh, that needs to be fixed to something else! I don't think i2c slave
functionality should be described in DT. The slave functionality is pure
software, so IMO it doesn't match the "HW description" requirement.

> But this works on the assumption that a I2C device registered via OF will
> always match a legacy I2C device ID and that the MODALIAS reported will
> always be of the form i2c:<device>.
> 
> And this could change in the future so the correct approach is to have an
> OF device ID table if the devices are registered via OF.
> 
> Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>

Thanks for finding the issue, still NAK to this patch. Are you
interested in updating the docs?


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Re: [PATCH] i2c: slave-eeprom: Add an OF device ID table

[Javier Martinez Canillas]

Hello Wolfram,

On 08/14/2017 09:52 PM, Wolfram Sang wrote:
> On Wed, Aug 09, 2017 at 12:12:56PM +0200, Javier Martinez Canillas wrote:
>> The driver doesn't have a struct of_device_id table but supported devices
>> are registered via Device Trees as shown in the following DT binding doc:
>>
>> Documentation/devicetree/bindings/i2c/i2c-designware.txt
> 
> Uhhh, that needs to be fixed to something else! I don't think i2c slave
> functionality should be described in DT. The slave functionality is pure
> software, so IMO it doesn't match the "HW description" requirement.
>

Right, indeed.
 
>> But this works on the assumption that a I2C device registered via OF will
>> always match a legacy I2C device ID and that the MODALIAS reported will
>> always be of the form i2c:<device>.
>>
>> And this could change in the future so the correct approach is to have an
>> OF device ID table if the devices are registered via OF.
>>
>> Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
> 
> Thanks for finding the issue, still NAK to this patch. Are you
> interested in updating the docs?
> 

What kind of change are you looking for? The example was introduced by commit
04606ccc84e3 ("i2c: designware: introducing I2C_SLAVE definitions") that says:

- A example was added to designware-core.txt Documentation that shows
  how the slave can be setup using DTS

So I could change this example to instead use a real EEPROM compatible (e.g:
"microchip,24c02") instead of "linux,slave-24c02". Would that be correct?

Best regards,
-- 
Javier Martinez Canillas
Software Engineer - Desktop Hardware Enablement
Red Hat

Re: [PATCH] i2c: slave-eeprom: Add an OF device ID table

[Wolfram Sang]

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> What kind of change are you looking for? The example was introduced by commit
> 04606ccc84e3 ("i2c: designware: introducing I2C_SLAVE definitions") that says:
> 
> - A example was added to designware-core.txt Documentation that shows
>   how the slave can be setup using DTS

My fault, I missed it :(

> So I could change this example to instead use a real EEPROM compatible (e.g:
> "microchip,24c02") instead of "linux,slave-24c02". Would that be correct?

I think this is Luis call how he'd like this to be changed. Given the
current discussion, I'd think it must be dropped entirely.

Luis?


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