linux-kernel - Re: [PATCH v2 4/7] i2c: i2c-core-acpi: Add i2c_acpi_dev

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Date:   Mon, 18 Jan 2021 11:18:55 +0200
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Daniel Scally <djrscally@...il.com>
Cc:     linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org,
        linux-gpio@...r.kernel.org, linux-i2c@...r.kernel.org,
        platform-driver-x86@...r.kernel.org, devel@...ica.org,
        rjw@...ysocki.net, lenb@...nel.org, andy@...nel.org,
        mika.westerberg@...ux.intel.com, linus.walleij@...aro.org,
        bgolaszewski@...libre.com, wsa@...nel.org, lee.jones@...aro.org,
        hdegoede@...hat.com, mgross@...ux.intel.com,
        robert.moore@...el.com, erik.kaneda@...el.com,
        sakari.ailus@...ux.intel.com, andriy.shevchenko@...ux.intel.com,
        kieran.bingham@...asonboard.com
Subject: Re: [PATCH v2 4/7] i2c: i2c-core-acpi: Add i2c_acpi_dev_name()

Hi Daniel,

Thank you for the patch.

On Mon, Jan 18, 2021 at 12:34:25AM +0000, Daniel Scally wrote:
> We want to refer to an i2c device by name before it has been

s/i2c device/acpi i2c device/ ?

> created by the kernel; add a function that constructs the name
> from the acpi device instead.
> 
> Signed-off-by: Daniel Scally <djrscally@...il.com>
> ---
> Changes in v2:
> 
> 	- Stopped using devm_kasprintf()
> 
>  drivers/i2c/i2c-core-acpi.c | 16 ++++++++++++++++
>  include/linux/i2c.h         |  5 +++++
>  2 files changed, 21 insertions(+)
> 
> diff --git a/drivers/i2c/i2c-core-acpi.c b/drivers/i2c/i2c-core-acpi.c
> index 37c510d9347a..98c3ba9a2350 100644
> --- a/drivers/i2c/i2c-core-acpi.c
> +++ b/drivers/i2c/i2c-core-acpi.c
> @@ -497,6 +497,22 @@ struct i2c_client *i2c_acpi_new_device(struct device *dev, int index,
>  }
>  EXPORT_SYMBOL_GPL(i2c_acpi_new_device);
>  
> +/**
> + * i2c_acpi_dev_name - Construct i2c device name for devs sourced from ACPI
> + * @adev:     ACPI device to construct the name for
> + *
> + * Constructs the name of an i2c device matching the format used by
> + * i2c_dev_set_name() to allow users to refer to an i2c device by name even
> + * before they have been instantiated.
> + *
> + * The caller is responsible for freeing the returned pointer.
> + */
> +char *i2c_acpi_dev_name(struct acpi_device *adev)
> +{
> +	return kasprintf(GFP_KERNEL, I2C_DEV_NAME_FORMAT, acpi_dev_name(adev));

There's a real danger of a memory leak, as the function name sounds very
similar to dev_name() or acpi_dev_name() and those don't allocate
memory. I'm not sure what a better name would be, but given that this
function is only used in patch 6/7 and not in the I2C subsystem itself,
I wonder if we should inline this kasprintf() call in the caller and
drop this patch.

> +}
> +EXPORT_SYMBOL_GPL(i2c_acpi_dev_name);
> +
>  #ifdef CONFIG_ACPI_I2C_OPREGION
>  static int acpi_gsb_i2c_read_bytes(struct i2c_client *client,
>  		u8 cmd, u8 *data, u8 data_len)
> diff --git a/include/linux/i2c.h b/include/linux/i2c.h
> index 4d40a4b46810..b82aac05b17f 100644
> --- a/include/linux/i2c.h
> +++ b/include/linux/i2c.h
> @@ -998,6 +998,7 @@ bool i2c_acpi_get_i2c_resource(struct acpi_resource *ares,
>  u32 i2c_acpi_find_bus_speed(struct device *dev);
>  struct i2c_client *i2c_acpi_new_device(struct device *dev, int index,
>  				       struct i2c_board_info *info);
> +char *i2c_acpi_dev_name(struct acpi_device *adev);
>  struct i2c_adapter *i2c_acpi_find_adapter_by_handle(acpi_handle handle);
>  #else
>  static inline bool i2c_acpi_get_i2c_resource(struct acpi_resource *ares,
> @@ -1014,6 +1015,10 @@ static inline struct i2c_client *i2c_acpi_new_device(struct device *dev,
>  {
>  	return ERR_PTR(-ENODEV);
>  }
> +static inline char *i2c_acpi_dev_name(struct acpi_device *adev)
> +{
> +	return NULL;
> +}
>  static inline struct i2c_adapter *i2c_acpi_find_adapter_by_handle(acpi_handle handle)
>  {
>  	return NULL;

-- 
Regards,

Laurent Pinchart