diff mbox series

[v6,1/8] i2c: core: let adapters be notified of client attach/detach

Message ID 20230105140307.272052-2-tomi.valkeinen@ideasonboard.com
State New
Headers
Series i2c-atr and FPDLink |

Commit Message

Tomi Valkeinen Jan. 5, 2023, 2:03 p.m. UTC 
  From: Luca Ceresoli <luca@lucaceresoli.net>

An adapter might need to know when a new device is about to be
added. This will soon bee needed to implement an "I2C address
translator" (ATR for short), a device that propagates I2C transactions
with a different slave address (an "alias" address). An ATR driver
needs to know when a slave is being added to find a suitable alias and
program the device translation map.

Add an attach/detach callback pair to allow adapter drivers to be
notified of clients being added and removed.

Signed-off-by: Luca Ceresoli <luca@lucaceresoli.net>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
---
 drivers/i2c/i2c-core-base.c | 21 ++++++++++++++++++++-
 include/linux/i2c.h         | 16 ++++++++++++++++
 2 files changed, 36 insertions(+), 1 deletion(-)

Comments

Laurent Pinchart Jan. 8, 2023, 3:13 a.m. UTC | #1 
Hi Tomi,

Thank you for the patch.

On Thu, Jan 05, 2023 at 04:03:00PM +0200, Tomi Valkeinen wrote:
> From: Luca Ceresoli <luca@lucaceresoli.net>
> 
> An adapter might need to know when a new device is about to be
> added. This will soon bee needed to implement an "I2C address
> translator" (ATR for short), a device that propagates I2C transactions
> with a different slave address (an "alias" address). An ATR driver
> needs to know when a slave is being added to find a suitable alias and
> program the device translation map.
> 
> Add an attach/detach callback pair to allow adapter drivers to be
> notified of clients being added and removed.

I've asked in the review of v6 if we could instead use the
BUS_NOTIFY_ADD_DEVICE and BUS_NOTIFY_DEL_DEVICE bus notifiers. There's
been a follow up discussion with Andy, but no reply from you AFAICS.
Have you given this a try ? It's not a mandatory requirement, but if it
can't be done (or shouldn't be done), I'd like to know why.

> Signed-off-by: Luca Ceresoli <luca@lucaceresoli.net>
> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
> ---
>  drivers/i2c/i2c-core-base.c | 21 ++++++++++++++++++++-
>  include/linux/i2c.h         | 16 ++++++++++++++++
>  2 files changed, 36 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
> index 7539b0740351..8a0888ba89e5 100644
> --- a/drivers/i2c/i2c-core-base.c
> +++ b/drivers/i2c/i2c-core-base.c
> @@ -916,6 +916,7 @@ int i2c_dev_irq_from_resources(const struct resource *resources,
>  struct i2c_client *
>  i2c_new_client_device(struct i2c_adapter *adap, struct i2c_board_info const *info)
>  {
> +	const struct i2c_attach_operations *attach_ops;
>  	struct i2c_client	*client;
>  	int			status;
>  
> @@ -967,15 +968,24 @@ i2c_new_client_device(struct i2c_adapter *adap, struct i2c_board_info const *inf
>  		}
>  	}
>  
> +	attach_ops = adap->attach_ops;
> +
> +	if (attach_ops && attach_ops->attach_client &&
> +	    attach_ops->attach_client(adap, info, client))
> +		goto out_remove_swnode;
> +
>  	status = device_register(&client->dev);
>  	if (status)
> -		goto out_remove_swnode;
> +		goto out_detach_client;
>  
>  	dev_dbg(&adap->dev, "client [%s] registered with bus id %s\n",
>  		client->name, dev_name(&client->dev));
>  
>  	return client;
>  
> +out_detach_client:
> +	if (attach_ops && attach_ops->detach_client)
> +		attach_ops->detach_client(adap, client);
>  out_remove_swnode:
>  	device_remove_software_node(&client->dev);
>  out_err_put_of_node:
> @@ -997,9 +1007,18 @@ EXPORT_SYMBOL_GPL(i2c_new_client_device);
>   */
>  void i2c_unregister_device(struct i2c_client *client)
>  {
> +	const struct i2c_attach_operations *attach_ops;
> +	struct i2c_adapter *adap;
> +
>  	if (IS_ERR_OR_NULL(client))
>  		return;
>  
> +	adap = client->adapter;
> +	attach_ops = adap->attach_ops;
> +
> +	if (attach_ops && attach_ops->detach_client)
> +		attach_ops->detach_client(adap, client);
> +
>  	if (client->dev.of_node) {
>  		of_node_clear_flag(client->dev.of_node, OF_POPULATED);
>  		of_node_put(client->dev.of_node);
> diff --git a/include/linux/i2c.h b/include/linux/i2c.h
> index f7c49bbdb8a1..9a385b6de388 100644
> --- a/include/linux/i2c.h
> +++ b/include/linux/i2c.h
> @@ -584,6 +584,21 @@ struct i2c_lock_operations {
>  	void (*unlock_bus)(struct i2c_adapter *adapter, unsigned int flags);
>  };
>  
> +/**
> + * struct i2c_attach_operations - callbacks to notify client attach/detach
> + * @attach_client: Notify of new client being attached
> + * @detach_client: Notify of new client being detached
> + *
> + * Both ops are optional.
> + */
> +struct i2c_attach_operations {
> +	int  (*attach_client)(struct i2c_adapter *adapter,
> +			      const struct i2c_board_info *info,
> +			      const struct i2c_client *client);
> +	void (*detach_client)(struct i2c_adapter *adapter,
> +			      const struct i2c_client *client);
> +};
> +
>  /**
>   * struct i2c_timings - I2C timing information
>   * @bus_freq_hz: the bus frequency in Hz
> @@ -726,6 +741,7 @@ struct i2c_adapter {
>  
>  	/* data fields that are valid for all devices	*/
>  	const struct i2c_lock_operations *lock_ops;
> +	const struct i2c_attach_operations *attach_ops;
>  	struct rt_mutex bus_lock;
>  	struct rt_mutex mux_lock;
>
Tomi Valkeinen Jan. 8, 2023, 9:24 a.m. UTC | #2 
On 08/01/2023 05:13, Laurent Pinchart wrote:
> Hi Tomi,
> 
> Thank you for the patch.
> 
> On Thu, Jan 05, 2023 at 04:03:00PM +0200, Tomi Valkeinen wrote:
>> From: Luca Ceresoli <luca@lucaceresoli.net>
>>
>> An adapter might need to know when a new device is about to be
>> added. This will soon bee needed to implement an "I2C address
>> translator" (ATR for short), a device that propagates I2C transactions
>> with a different slave address (an "alias" address). An ATR driver
>> needs to know when a slave is being added to find a suitable alias and
>> program the device translation map.
>>
>> Add an attach/detach callback pair to allow adapter drivers to be
>> notified of clients being added and removed.
> 
> I've asked in the review of v6 if we could instead use the
> BUS_NOTIFY_ADD_DEVICE and BUS_NOTIFY_DEL_DEVICE bus notifiers. There's
> been a follow up discussion with Andy, but no reply from you AFAICS.
> Have you given this a try ? It's not a mandatory requirement, but if it
> can't be done (or shouldn't be done), I'd like to know why.

Sorry, I meant to mention this in the cover letter, but forgot:

I haven't looked at the bus notifiers yet, but will have a look. I 
wanted to send a new revision due to the large amount of changes already 
done.

  Tomi
diff mbox series

Patch

diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
index 7539b0740351..8a0888ba89e5 100644
--- a/drivers/i2c/i2c-core-base.c
+++ b/drivers/i2c/i2c-core-base.c
@@ -916,6 +916,7 @@  int i2c_dev_irq_from_resources(const struct resource *resources,
 struct i2c_client *
 i2c_new_client_device(struct i2c_adapter *adap, struct i2c_board_info const *info)
 {
+	const struct i2c_attach_operations *attach_ops;
 	struct i2c_client	*client;
 	int			status;
 
@@ -967,15 +968,24 @@  i2c_new_client_device(struct i2c_adapter *adap, struct i2c_board_info const *inf
 		}
 	}
 
+	attach_ops = adap->attach_ops;
+
+	if (attach_ops && attach_ops->attach_client &&
+	    attach_ops->attach_client(adap, info, client))
+		goto out_remove_swnode;
+
 	status = device_register(&client->dev);
 	if (status)
-		goto out_remove_swnode;
+		goto out_detach_client;
 
 	dev_dbg(&adap->dev, "client [%s] registered with bus id %s\n",
 		client->name, dev_name(&client->dev));
 
 	return client;
 
+out_detach_client:
+	if (attach_ops && attach_ops->detach_client)
+		attach_ops->detach_client(adap, client);
 out_remove_swnode:
 	device_remove_software_node(&client->dev);
 out_err_put_of_node:
@@ -997,9 +1007,18 @@  EXPORT_SYMBOL_GPL(i2c_new_client_device);
  */
 void i2c_unregister_device(struct i2c_client *client)
 {
+	const struct i2c_attach_operations *attach_ops;
+	struct i2c_adapter *adap;
+
 	if (IS_ERR_OR_NULL(client))
 		return;
 
+	adap = client->adapter;
+	attach_ops = adap->attach_ops;
+
+	if (attach_ops && attach_ops->detach_client)
+		attach_ops->detach_client(adap, client);
+
 	if (client->dev.of_node) {
 		of_node_clear_flag(client->dev.of_node, OF_POPULATED);
 		of_node_put(client->dev.of_node);
diff --git a/include/linux/i2c.h b/include/linux/i2c.h
index f7c49bbdb8a1..9a385b6de388 100644
--- a/include/linux/i2c.h
+++ b/include/linux/i2c.h
@@ -584,6 +584,21 @@  struct i2c_lock_operations {
 	void (*unlock_bus)(struct i2c_adapter *adapter, unsigned int flags);
 };
 
+/**
+ * struct i2c_attach_operations - callbacks to notify client attach/detach
+ * @attach_client: Notify of new client being attached
+ * @detach_client: Notify of new client being detached
+ *
+ * Both ops are optional.
+ */
+struct i2c_attach_operations {
+	int  (*attach_client)(struct i2c_adapter *adapter,
+			      const struct i2c_board_info *info,
+			      const struct i2c_client *client);
+	void (*detach_client)(struct i2c_adapter *adapter,
+			      const struct i2c_client *client);
+};
+
 /**
  * struct i2c_timings - I2C timing information
  * @bus_freq_hz: the bus frequency in Hz
@@ -726,6 +741,7 @@  struct i2c_adapter {
 
 	/* data fields that are valid for all devices	*/
 	const struct i2c_lock_operations *lock_ops;
+	const struct i2c_attach_operations *attach_ops;
 	struct rt_mutex bus_lock;
 	struct rt_mutex mux_lock;