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Subject[RFC][PATCH][TRIVIAL] System ACE fails in look for root devices
Date
From
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;

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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