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SubjectRe: [RFC][PATCH][TRIVIAL] System ACE fails in look for root devices
On Thu, Oct 13, 2011 at 01:02:42PM +0200, Petr Cvek wrote:
> Hello,
>
> I sent this mail some time ago, but nobody replied :-(.
>
>
> I'm using microblaze linux on ML506 board and I found problem with
> SystemACE CF driver.
>
> When xsysace driver is probed, and dts file does not include entry
> "port-number" (existence of line not actually tested) on line:
>
> of_property_read_u32(dev->dev.of_node, "port-number", &id);
>
> kernel fails to boot with this message:
>
> <4>VFS: Cannot open root device "xsa2" or unknown-block(0,0)
> <4>Please append a correct "root=" boot option; here are the
> available partitions:
> <4>fff:ffff0 990864 xs` (driver?)
> <4> fff:ffff1 124960 xs`1 00000000-0000-0000-0000-000000000000
> <4> fff:ffff2 865872 xs`2 00000000-0000-0000-0000-000000000000
> <0>Kernel panic - not syncing: VFS: Unable to mount root fs on
> unknown-block(0,0)
>
> (note xs` xs`1 xs`2 partition names)
>
> So I've done some searching and found "ace->id" variable, which has
> value "-1". Because this value define letter of drive and is
> incremented by 'a', then with its value of -1, creates letter before
> 'a' thus '`'.
>
> "ace->id" value is assigned in ace_probe function on line
>
> of_property_read_u32(dev->dev.of_node, "port-number", &id);
> if (id < 0)
> id = 0;

However, of_property_read_u32() can only accept a u32 value, not an
int, so this needs to be solved with two variables to be correct:

int id;
u32 tmp;
id = dev->id;
if (of_property_read_u32(dev->dev.of_node, "port-number", &tmp)
id = tmp;
if (id < 0)
id = 0;

It's not as pretty, but it is a limitation of how of_property_read_u32
has to be implemented. I hope to find a better way to do it that
doesn't have the u32 restriction on the return value.

g.


>
> This condition should prevents value to be less than zero, but is
> does not. It's because type, which is u32 few lines before,
> condition is never true. So I suggest changing it to int. Actually,
> there was patch some time ago, which has changed it into u32 (last
> patch for xsysace.c).
>
> http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=commitdiff;h=5d10302f46df1d9a85c34ea97f9b6c29e414482e
>
> And finally here is my patch, which suggests changing this line back:
>
> Test for signed value is never true, because of unsigned type.
>
> From: Petr Cvek <petr.cvek@tul.cz>
>
> Signed-off-by: Petr Cvek <petr.cvek@tul.cz>
> ---
> diff --git a/drivers/block/xsysace.c b/drivers/block/xsysace.c
> index fb1975d..3ed920c 100644
> --- a/drivers/block/xsysace.c
> +++ b/drivers/block/xsysace.c
> @@ -1155,7 +1155,7 @@ static int __devinit ace_probe(struct
> platform_device *dev)
> {
> resource_size_t physaddr = 0;
> int bus_width = ACE_BUS_WIDTH_16; /* FIXME: should not be hard
> coded */
> - u32 id = dev->id;
> + int id = dev->id;
> int irq = NO_IRQ;
> int i;
>


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