Re: [Qemu-devel] [PATCH V5 5/7] Add max device width parameter for NOR devices

[Peter Maydell]

On 12 December 2013 17:26, Peter Maydell <address@hidden> wrote:
> On 5 December 2013 21:35, Roy Franz <address@hidden> wrote:
>> For handling CFI and device ID reads, we need to not only know the
>> width that a NOR flash device is configured for, but also its maximum
>> width.  The maximum width addressing mode is used for multi-width
>> parts no matter which width they are configured for.  The most common
>> case is x16 parts that also support x8 mode.  When configured for x8
>> operation these devices respond to CFI and device ID requests differently
>> than native x8 NOR parts.
>
>>      DEFINE_PROP_UINT64("sector-length", struct pflash_t, sector_len, 0),
>>      DEFINE_PROP_UINT8("width", struct pflash_t, bank_width, 0),
>>      DEFINE_PROP_UINT8("device-width", struct pflash_t, device_width, 0),
>> +    DEFINE_PROP_UINT8("max-device-width", struct pflash_t, 
>> max_device_width, 0),
>
> So I think that given we now have three width related properties
> we could use a comment here about what they mean. Do I have
> this right?
>
> /* width here is the overall width of this QEMU device in bytes.
>  * The QEMU device may be emulating a number of flash devices
>  * wired up in parallel; the width of each individual flash
>  * device should be specified via device-width. If the individual
>  * devices have a maximum width which is greater than the width
>  * they are being used for, this maximum width should be set via
>  * max-device-width (which otherwise defaults to device-width).
>  * So for instance a 32-bit wide QEMU flash device made from four
>  * 16-bit flash devices used in 8-bit wide mode would be configured
>  * with width = 4, device-width = 1, max-device-width = 2.
>  *
>  * If device-width is not specified we default to backwards
>  * compatible behaviour which is a bad emulation of two
>  * 16 bit devices making up a 32 bit wide QEMU device. This
>  * is deprecated for new uses of this device.
>  */

PS: if you're happy that the comment above is correct, I
can just add it locally (and fix up the format nits in
the other patch), to save you having to respin the series,
and stick it in the target-arm.next queue.

thanks
-- PMM