[alsa-devel] [RFC] i2c: Revert back to old device naming for ACPI enumerated I2C slaves

[Wolfram Sang]

On Fri, Oct 02, 2015 at 12:27:16PM +0300, Jarkko Nikula wrote:
> On 10/01/2015 11:37 PM, Wolfram Sang wrote:
> >
> >>This is for discussion so I didn't cc stable at vger.kernel.org yet. I was
> >>thinking would it work if we'd keep the stable name but have an another
> >>symlink in /sys/bus/i2c/devices/ that uses "x-00yz" name. However this
> >>feels ill-use of devices directory and probably causes more troubles
> >>elsewhere.
> >
> >Do you foresee troubles already? I am still in favour of a symlink.
> >
> I haven't looked at this for a while but one problem was that devices/
> directory belongs to private structure of struct bus_type and in order to
> create a symlink there it needs to done in drivers/base/bus.c:
> bus_add_device() which felt quite hackish to me.

This is just a quick prototype and untested; but I did something similar
in the i2c-mux code:

diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
index 5f89f1e3c2f24f..715dca57ba68fd 100644
--- a/drivers/i2c/i2c-core.c
+++ b/drivers/i2c/i2c-core.c
@@ -970,13 +970,15 @@ static void i2c_dev_set_name(struct i2c_adapter *adap,
 {
 	struct acpi_device *adev = ACPI_COMPANION(&client->dev);
 
-	if (adev) {
-		dev_set_name(&client->dev, "i2c-%s", acpi_dev_name(adev));
-		return;
-	}
-
 	dev_set_name(&client->dev, "%d-%04x", i2c_adapter_id(adap),
 		     i2c_encode_flags_to_addr(client));
+
+	if (adev) {
+		char symlink_name[256];
+
+		snprintf(symlink_name, sizeof(symlink_name), "i2c-%s", acpi_dev_name(adev));
+		sysfs_create_link(&client->dev.kobj, &adap->dev.kobj, symlink_name);
+	}
 }
 
 /**

Shouldn't something like this be enough?

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