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    SubjectRe: [PATCH v3] arch/tile: add hypervisor-based character driver for SPI flash ROM
    On Thursday 02 June 2011, Chris Metcalf wrote:
    > 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 <>

    Reviewed-by: Arnd Bergmann <>

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      Last update: 2011-06-10 18:43    [W:0.027 / U:7.300 seconds]
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