mtd: spi-nor: sysfs: hide manufacturer if it is not set

The manufacturer may be optional when pure SFDP flashes are supported.
Hide the sysfs property if no manufacturer is set.
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/20220810220654.1297699-3-michael@walle.cc

Documentation/ABI/testing/sysfs-bus-spi-devices-spi-nor

@@ -15,6 +15,9 @@ KernelVersion:	5.14
 Contact:	linux-mtd@lists.infradead.org
 Description:	(RO) Manufacturer of the SPI NOR flash.
 
+		The attribute is not present if the flash device isn't
+		known to the kernel and is only probed by its SFDP
+		tables.
 
 What:		/sys/bus/spi/devices/.../spi-nor/partname
 Date:		April 2021

drivers/mtd/spi-nor/sysfs.c

@@ -74,6 +74,8 @@ static umode_t spi_nor_sysfs_is_visible(struct kobject *kobj,
 	struct spi_mem *spimem = spi_get_drvdata(spi);
 	struct spi_nor *nor = spi_mem_get_drvdata(spimem);
 
+	if (attr == &dev_attr_manufacturer.attr && !nor->manufacturer)
+		return 0;
 	if (attr == &dev_attr_jedec_id.attr && !nor->info->id_len)
 		return 0;