mtd: spi-nor: remember full JEDEC flash ID

At the moment, we print the JEDEC ID that is stored in our database. The
generic flash support won't have such an entry in our database. To find
out the JEDEC ID later we will have to cache it. There is also another
advantage: If the flash is found in the database, the ID could be
truncated because the ID of the entry is used which can be shorter. Some
flashes still holds valuable information in the bytes after the JEDEC ID
and come in handy during debugging of when coping with INFO6() entries.
These are not accessible for now.

Save a copy of the ID bytes after reading and display it via debugfs.
Signed-off-by: Michael Walle <michael@walle.cc>
Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Reviewed-by: Takahiro Kuwano <Takahiro.Kuwano@infineon.com>
Link: https://lore.kernel.org/r/20220810220654.1297699-4-michael@walle.cc

drivers/mtd/spi-nor/core.c

@@ -1666,6 +1666,11 @@ static const struct flash_info *spi_nor_detect(struct spi_nor *nor)
 		return ERR_PTR(ret);
 	}
 
+	/* Cache the complete flash ID. */
+	nor->id = devm_kmemdup(nor->dev, id, SPI_NOR_MAX_ID_LEN, GFP_KERNEL);
+	if (!nor->id)
+		return ERR_PTR(-ENOMEM);
+
 	info = spi_nor_match_id(nor, id);
 	if (!info) {
 		dev_err(nor->dev, "unrecognized JEDEC id bytes: %*ph\n",

drivers/mtd/spi-nor/debugfs.c

@@ -81,7 +81,7 @@ static int spi_nor_params_show(struct seq_file *s, void *data)
 	int i;
 
 	seq_printf(s, "name\t\t%s\n", info->name);
-	seq_printf(s, "id\t\t%*ph\n", info->id_len, info->id);
+	seq_printf(s, "id\t\t%*ph\n", SPI_NOR_MAX_ID_LEN, nor->id);
 	string_get_size(params->size, 1, STRING_UNITS_2, buf, sizeof(buf));
 	seq_printf(s, "size\t\t%s\n", buf);
 	seq_printf(s, "write size\t%u\n", params->writesize);

include/linux/mtd/spi-nor.h

@@ -349,6 +349,8 @@ struct spi_nor_flash_parameter;
  * @bouncebuf:		bounce buffer used when the buffer passed by the MTD
  *                      layer is not DMA-able
  * @bouncebuf_size:	size of the bounce buffer
+ * @id:			The flash's ID bytes. Always contains
+ *			SPI_NOR_MAX_ID_LEN bytes.
  * @info:		SPI NOR part JEDEC MFR ID and other info
  * @manufacturer:	SPI NOR manufacturer
  * @addr_nbytes:	number of address bytes
@@ -379,6 +381,7 @@ struct spi_nor {
 	struct spi_mem		*spimem;
 	u8			*bouncebuf;
 	size_t			bouncebuf_size;
+	u8			*id;
 	const struct flash_info	*info;
 	const struct spi_nor_manufacturer *manufacturer;
 	u8			addr_nbytes;