> On Sat, Apr 13, 2013 at 08:21:39AM +0400, Alexander Shiyan wrote:
> > +static void __init clps711x_add_gpio(void)
> > +{
> > + const struct resource clps711x_gpio0_res[] = {
> > + DEFINE_RES_MEM(PADR, SZ_1),
> > + DEFINE_RES_MEM(PADDR, SZ_1),
> > + };
...
> Don't do this - this is incredibly wasteful.
>
> C lesson 1: do not put unmodified initialised structures onto the stack.
>
> What the C compiler will do with the above is exactly the same as this
> for each structure:
>
> static const struct resource private_clps711x_gpio4_res[] = {
> DEFINE_RES_MEM(PEDR, SZ_1),
> DEFINE_RES_MEM(PEDDR, SZ_1),
> };
>
> static void __init clps711x_add_gpio(void)
> {
> const struct resource clps711x_gpio4_res[] = private_clps711x_gpio4_res;
> ...
>
> which will in itself be a call out to memcpy, or an inlined memcpy. Now
> do you see why it's wasteful? You might as well write the thing in that
> way to start with and safe the additional code to copy the structures.
>
> The other way to do this, which will probably be far more space efficient:
>
> static phys_addr_t gpio_addrs[][2] = {
> { PADR, PADDR },
> { PBDR, PBDDR },
> ...
> };
>
> static void __init clps711x_add_gpio(void)
> {
> struct resource gpio_res[2];
> unsigned i;
>
> gpio_res[0].flags = IORESOURCE_MEM;
> gpio_res[1].flags = IORESOURCE_MEM;
>
> for (i = 0; i < ARRAY_SIZE(gpio_addrs); i++) {
> gpio_res[0].start = gpio_addrs[i][0];
> gpio_res[0].end = gpio_res[0].start;
> gpio_res[1].start = gpio_addrs[i][1];
> gpio_res[1].end = gpio_res[1].start;
>
> platform_device_register_simple("clps711x-gpio", i,
> gpio_res, ARRAY_SIZE(gpio_res));
> }
> }
>
> which results in smaller storage and most probably also smaller code size
> too.
Very strange results with this change.
So, I add a debug output before "platform_device_register_simple" for
print resource and in "__request_resource" for print parent.
This is output.
gpio 0 [mem 0x80000000] [mem 0x80000040]
resource: root [??? 0xe3a0f000-0x00000000 flags 0xb00000]
clps711x-gpio.0: failed to claim resource 0
The first line is seems correct. But I do not understand why
parent is wrong here. Normally it should be as:
resource: root [mem 0x00000000-0xffffffff].
And it shows normal with my first version.
Have anyone any ideas?
Thanks.
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