[PATCH 6.1.y 1/3] i2c: core: Introduce i2c_client_get_device_id helper function

[Sasha Levin <sashal@kernel.org>]

From: Angel Iglesias <ang.iglesiasg@gmail.com>

[ Upstream commit 662233731d66cf41e7494e532e702849c8ce18f3 ]

Introduces new helper function to aid in .probe_new() refactors. In order
to use existing i2c_get_device_id() on the probe callback, the device
match table needs to be accessible in that function, which would require
bigger refactors in some drivers using the deprecated .probe callback.

This issue was discussed in more detail in the IIO mailing list.

Link: https://lore.kernel.org/all/20221023132302.911644-11-u.kleine-koenig@pengutronix.de/
Suggested-by: Nuno Sá <noname.nuno@gmail.com>
Suggested-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Suggested-by: Jonathan Cameron <jic23@kernel.org>
Signed-off-by: Angel Iglesias <ang.iglesiasg@gmail.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>
Stable-dep-of: 4e4b9f5ce9df ("power: supply: max17040: drop incorrect I2C functionality check")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/i2c/i2c-core-base.c | 14 ++++++++++++++
 include/linux/i2c.h         |  1 +
 2 files changed, 15 insertions(+)

diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
index ade12c0b1006c..588424db22a22 100644
--- a/drivers/i2c/i2c-core-base.c
+++ b/drivers/i2c/i2c-core-base.c
@@ -2426,6 +2426,20 @@ int i2c_get_device_id(const struct i2c_client *client,
 }
 EXPORT_SYMBOL_GPL(i2c_get_device_id);
 
+/**
+ * i2c_client_get_device_id - get the driver match table entry of a device
+ * @client: the device to query. The device must be bound to a driver
+ *
+ * Returns a pointer to the matching entry if found, NULL otherwise.
+ */
+const struct i2c_device_id *i2c_client_get_device_id(const struct i2c_client *client)
+{
+	const struct i2c_driver *drv = to_i2c_driver(client->dev.driver);
+
+	return i2c_match_id(drv->id_table, client);
+}
+EXPORT_SYMBOL_GPL(i2c_client_get_device_id);
+
 /* ----------------------------------------------------
  * the i2c address scanning function
  * Will not work for 10-bit addresses!
diff --git a/include/linux/i2c.h b/include/linux/i2c.h
index 87b403a6d7e41..60c5bc674dcce 100644
--- a/include/linux/i2c.h
+++ b/include/linux/i2c.h
@@ -189,6 +189,7 @@ s32 i2c_smbus_read_i2c_block_data_or_emulated(const struct i2c_client *client,
 					      u8 *values);
 int i2c_get_device_id(const struct i2c_client *client,
 		      struct i2c_device_identity *id);
+const struct i2c_device_id *i2c_client_get_device_id(const struct i2c_client *client);
 #endif /* I2C */
 
 /**
-- 
2.53.0