[RFC PATCH 2/2] i2c: mux: pca954x: verify the device id of the pca984x chips

[Peter Rosin <peda@axentia.se>]

Make sure to not disallow the chips on adapters that are not capable
of reading the device id.

Signed-off-by: Peter Rosin <peda@axentia.se>
---
 drivers/i2c/muxes/i2c-mux-pca954x.c | 43 +++++++++++++++++++++++++++++++++++++
 1 file changed, 43 insertions(+)

diff --git a/drivers/i2c/muxes/i2c-mux-pca954x.c b/drivers/i2c/muxes/i2c-mux-pca954x.c
index fbb84c7ef282..ff0c7a144fbb 100644
--- a/drivers/i2c/muxes/i2c-mux-pca954x.c
+++ b/drivers/i2c/muxes/i2c-mux-pca954x.c
@@ -77,6 +77,7 @@ struct chip_desc {
 		pca954x_ismux = 0,
 		pca954x_isswi
 	} muxtype;
+	struct i2c_device_identity id;
 };
 
 struct pca954x {
@@ -97,59 +98,83 @@ static const struct chip_desc chips[] = {
 		.nchans = 2,
 		.enable = 0x4,
 		.muxtype = pca954x_ismux,
+		.id = { .manufacturer_id = I2C_DEVICE_ID_NONE },
 	},
 	[pca_9542] = {
 		.nchans = 2,
 		.enable = 0x4,
 		.has_irq = 1,
 		.muxtype = pca954x_ismux,
+		.id = { .manufacturer_id = I2C_DEVICE_ID_NONE },
 	},
 	[pca_9543] = {
 		.nchans = 2,
 		.has_irq = 1,
 		.muxtype = pca954x_isswi,
+		.id = { .manufacturer_id = I2C_DEVICE_ID_NONE },
 	},
 	[pca_9544] = {
 		.nchans = 4,
 		.enable = 0x4,
 		.has_irq = 1,
 		.muxtype = pca954x_ismux,
+		.id = { .manufacturer_id = I2C_DEVICE_ID_NONE },
 	},
 	[pca_9545] = {
 		.nchans = 4,
 		.has_irq = 1,
 		.muxtype = pca954x_isswi,
+		.id = { .manufacturer_id = I2C_DEVICE_ID_NONE },
 	},
 	[pca_9546] = {
 		.nchans = 4,
 		.muxtype = pca954x_isswi,
+		.id = { .manufacturer_id = I2C_DEVICE_ID_NONE },
 	},
 	[pca_9547] = {
 		.nchans = 8,
 		.enable = 0x8,
 		.muxtype = pca954x_ismux,
+		.id = { .manufacturer_id = I2C_DEVICE_ID_NONE },
 	},
 	[pca_9548] = {
 		.nchans = 8,
 		.muxtype = pca954x_isswi,
+		.id = { .manufacturer_id = I2C_DEVICE_ID_NONE },
 	},
 	[pca_9846] = {
 		.nchans = 4,
 		.muxtype = pca954x_isswi,
+		.id = {
+			.manufacturer_id = I2C_DEVICE_ID_NXP_SEMICONDUCTORS,
+			.part_id = 0x10b,
+		},
 	},
 	[pca_9847] = {
 		.nchans = 8,
 		.enable = 0x8,
 		.muxtype = pca954x_ismux,
+		.id = {
+			.manufacturer_id = I2C_DEVICE_ID_NXP_SEMICONDUCTORS,
+			.part_id = 0x108,
+		},
 	},
 	[pca_9848] = {
 		.nchans = 8,
 		.muxtype = pca954x_isswi,
+		.id = {
+			.manufacturer_id = I2C_DEVICE_ID_NXP_SEMICONDUCTORS,
+			.part_id = 0x10a,
+		},
 	},
 	[pca_9849] = {
 		.nchans = 4,
 		.enable = 0x4,
 		.muxtype = pca954x_ismux,
+		.id = {
+			.manufacturer_id = I2C_DEVICE_ID_NXP_SEMICONDUCTORS,
+			.part_id = 0x109,
+		},
 	},
 };
 
@@ -384,6 +409,24 @@ static int pca954x_probe(struct i2c_client *client,
 	else
 		data->chip = &chips[id->driver_data];
 
+	if (data->chip->id.manufacturer_id != I2C_DEVICE_ID_NONE) {
+		struct i2c_device_identity id;
+
+		ret = i2c_get_device_id(client, &id);
+		if (ret && ret != -EOPNOTSUPP)
+			return ret;
+
+		if (!ret &&
+		    (id.manufacturer_id != data->chip->id.manufacturer_id ||
+		     id.part_id != data->chip->id.part_id)) {
+			dev_warn(&client->dev,
+				 "unexpected device id %03x-%03x-%x\n",
+				 id.manufacturer_id, id.part_id,
+				 id.die_revision);
+			return -ENODEV;
+		}
+	}
+
 	data->last_chan = 0;		   /* force the first selection */
 
 	idle_disconnect_dt = of_node &&
-- 
2.11.0