|author||Chris Metcalf <email@example.com>||2011-06-10 13:07:48 -0400|
|committer||Chris Metcalf <firstname.lastname@example.org>||2011-06-10 13:07:48 -0400|
arch/tile: add hypervisor-based character driver for SPI flash ROM
The first version of this patch proposed an arch/tile/drivers/ directory, but the consensus was that this was probably a poor choice for a place to group Tilera-specific drivers, and that in any case grouping by platform was discouraged, and grouping by function was preferred. This version of the patch addresses various issues raised in the community, primarily the absence of sysfs integration. The sysfs integration now handles passing information on sector size, page size, and total partition size to userspace as well. In addition, we now use a single "struct cdev" to manage all the partition minor devices, and dynamically discover the correct number of partitions from the hypervisor rather than using a module_param with a default value. This driver has no particular "peer" drivers it can be grouped with. It is sort of like an MTD driver for SPI ROM, but it doesn't group well with the other MTD devices since it relies on hypervisor virtualization to handle many of the irritating aspects of flash ROM management: sector awareness, background read for sub-sector writes, bit examination to determine whether a sector erase needs to be issued, etc. It is in fact more like an EEPROM driver, but the hypervisor virtualization does require a "flush" command if you wish to commit a sector write prior to writing to a different sector, and this is sufficiently different from generic I2C/SPI EEPROMs that as a result it doesn't group well with them either. The simple character device is already in use by a range of Tilera SPI ROM management tools, as well as by customers. In addition, using the simple character device actually simplifies the userspace tools, since they don't need to manage sector erase, background read, etc. This both simplifies the code (since we can uniformly manage plain files and the SPI ROM) as well as makes the user code portable to non-Linux platforms that don't offer the same MTD ioctls. Signed-off-by: Chris Metcalf <email@example.com> Reviewed-by: Arnd Bergmann <firstname.lastname@example.org>
Diffstat (limited to 'drivers/char/Kconfig')
1 files changed, 11 insertions, 0 deletions
diff --git a/drivers/char/Kconfig b/drivers/char/Kconfig
index 49502bc5360..423fd56bf61 100644
@@ -616,5 +616,16 @@ config MSM_SMD_PKT
Enables userspace clients to read and write to some packet SMD
ports via device interface for MSM chipset.
+ bool "Character-device access via hypervisor to the Tilera SPI ROM"
+ depends on TILE
+ default y
+ This device provides character-level read-write access
+ to the SROM, typically via the "0", "1", and "2" devices
+ in /dev/srom/. The Tilera hypervisor makes the flash
+ device appear much like a simple EEPROM, and knows
+ how to partition a single ROM for multiple purposes.