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    SubjectRe: [PATCH] virtio-mmio: Devices parameter parsing
    On Tue, 2011-11-22 at 00:53 +0000, Rusty Russell wrote:
    > > Any ideas?
    > Perhaps not today. So, we will need a linked list of devices and
    > resources. Yeah, that means allocating, which means YA
    > slab_is_available()/alloc_bootmem() hack.

    Hm. It doesn't sound like a good deal, really... Loads of tricks to get
    data I need quite late in the boot process...

    > Think of yourself as a pioneer...

    I had a vague idea of "late parameters" last night, which would be
    parsed once whole machinery is up and running. Will look around and try
    to propose something.

    On Tue, 2011-11-22 at 00:44 +0000, Rusty Russell wrote:
    > Or would it be simpler to enhance sscanf() with some weird format option
    > for suffixing? I haven't looked for similar cases, but I'd suspect a
    > big win in general.
    > This would be neater than anything else we've got:
    > if (sscanf(device, "%llu@%llu[KMG]:%u", ...) != 3
    > && sscanf(device, "%llu@%llu[KMG]:%u:%u", ...) != 4)
    > return -EINVAL;

    sscanf was a good hint! Thanks, why haven't I thought of it myself? ;-)

    That's what I came up with:

    static int vm_cmdline_set(const char *device,
    const struct kernel_param *kp)
    struct resource resources[2] = {};
    char *str;
    long long int base;
    int processed, consumed = 0;
    struct platform_device *pdev;

    resources[0].flags = IORESOURCE_MEM;
    resources[1].flags = IORESOURCE_IRQ;

    resources[0].end = memparse(device, &str) - 1;

    processed = sscanf(str, "@%lli:%u%n:%d%n",
    &base, &resources[1].start, &consumed,
    &vm_cmdline_id, &consumed);

    if (processed < 2 || processed > 3 || str[consumed])
    return -EINVAL;

    resources[0].start = base;
    resources[0].end += base;
    resources[1].end = resources[1].start;

    The only bit missing from sscanf() would be some sort of "%m" format,
    which behaved like memparse and also processed unsigned number with "0
    base" (hard to believe but the only "universal" - as in octal, dec and
    hex - format is %i, which is signed). But still, looks quite neat
    already :-)

    I'll try to have a look at the "late parameters" idea tomorrow. Any
    early warnings?



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