From: Benjamin Szőke <[email protected]>
Optionally, an I2C controller may have a "linux,i2c-dev-name" property.
This is a string which is defining a custom suffix name for I2C device
in /dev/i2c-<name> format. It helps to improve software portability between
various SoCs and reduce complexities of hardware related codes in SWs.
Signed-off-by: Benjamin Szőke <[email protected]>
---
drivers/i2c/i2c-dev.c | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)
diff --git a/drivers/i2c/i2c-dev.c b/drivers/i2c/i2c-dev.c
index 8b7e599f1674..df4cec88ea59 100644
--- a/drivers/i2c/i2c-dev.c
+++ b/drivers/i2c/i2c-dev.c
@@ -651,6 +651,7 @@ static void i2cdev_dev_release(struct device *dev)
static int i2cdev_attach_adapter(struct device *dev)
{
+ const char *name;
struct i2c_adapter *adap;
struct i2c_dev *i2c_dev;
int res;
@@ -672,7 +673,16 @@ static int i2cdev_attach_adapter(struct device *dev)
i2c_dev->dev.parent = &adap->dev;
i2c_dev->dev.release = i2cdev_dev_release;
- res = dev_set_name(&i2c_dev->dev, "i2c-%d", adap->nr);
+ /*
+ * If "linux,i2c-dev-name" is specified in device tree, use /dev/i2c-<name>
+ * in Linux userspace, otherwise use /dev/i2c-<nr>.
+ */
+ res = device_property_read_string(&adap->dev, "linux,i2c-dev-name", &name);
+ if (res < 0)
+ res = dev_set_name(&i2c_dev->dev, "i2c-%d", adap->nr);
+ else
+ res = dev_set_name(&i2c_dev->dev, "i2c-%s", name);
+
if (res)
goto err_put_i2c_dev;
--
2.39.3
> Optionally, an I2C controller may have a "linux,i2c-dev-name" property.
> This is a string which is defining a custom suffix name for I2C device
> in /dev/i2c-<name> format. It helps to improve software portability between
> various SoCs and reduce complexities of hardware related codes in SWs.
(I thought I already replied to this?)
Highly similar to [1] from 2021. I don't have a super clear opinion
about this, so I'd need help from the DT maintainers. But the discussion
from back then stalled.
[1] http://patchwork.ozlabs.org/project/linux-i2c/list/?series=237908
On Wed, May 29, 2024 at 12:28:03PM +0200, Wolfram Sang wrote:
>
> > Optionally, an I2C controller may have a "linux,i2c-dev-name" property.
> > This is a string which is defining a custom suffix name for I2C device
> > in /dev/i2c-<name> format. It helps to improve software portability between
> > various SoCs and reduce complexities of hardware related codes in SWs.
>
> (I thought I already replied to this?)
>
> Highly similar to [1] from 2021. I don't have a super clear opinion
> about this, so I'd need help from the DT maintainers. But the discussion
> from back then stalled.
>
> [1] http://patchwork.ozlabs.org/project/linux-i2c/list/?series=237908
This patch (or one very similar) got sent to the SPI and GPIO subsystems
too. The response was effectively "use udev":
https://lore.kernel.org/all/[email protected]/
https://lore.kernel.org/all/[email protected]/
This definitely is in "devicetree properties are not for software-policy"
territory to me, maybe Rob's changed his mind since 2021.