Re: [PATCH 3/3] ppc/uImage: Add support for RAM Disks

[Sebastian Andrzej Siewior <bigeasy@linutronix.de>]

On 01/17/2013 10:47 AM, Suzuki K. Poulose wrote:
>>> +{
>>> +    struct Image_info img;
>>> +    off_t size;
>>> +    const unsigned char *buf =
>>> +            (const unsigned char *)slurp_file(filename, &size);
>>
>> is the const cast required here?
> 
> Yes, the uImage_probe() expects (const unsigned char *) as the first
> argument.

That is okay, you can pass a non-const pointer to function that expects
a const pointer. You just can't pass a const pointer to a non-const
function and you should not cast in that situtation as well.

>>> +        buf = img.buf;
>>> +        size = img.len;
>>> +    }
>>> +
>>> +    *r_size = size;
>>> +    return buf;
>>> +}
>>> +   
>>> int uImage_ppc_probe(const char *buf, off_t len)
>>> {
>>>     int type;
>>> @@ -196,7 +216,7 @@ static int ppc_load_bare_bits(int argc, char
>>> **argv, const char *buf,
>>>     blob_buf = fixup_dtb_init(info, blob_buf, &blob_size, load_addr,
>>> &dtb_addr);
>>>
>>>     if (ramdisk) {
>>> -        seg_buf = slurp_file(ramdisk, &seg_size);
>>> +        seg_buf = slurp_ramdisk_ppc(ramdisk, &seg_size);
>>
>> I'm not sure but this kinda breaks the case where someone was using a
>> plain file without the uImage header. I don't know if someone used this
>> at all but it seems we have code for this. The way you load the uImage
>> is very generic and I would expect to load it the same way on ARM or SH.
>>
> If the ramdisk doesn't have uImage header, the slurp_ramdisk_ppc()
> defaults to the original behaviour. i.e, it just does a slurp_file()
> as it used to do earlier.
that is okay then.

>> One thing that is different compared to kernel: If the compression is
>> set to GZ on a ramdisk image you should not uncompress it. I think that
>> uImage_load() decompresses the .gz part for you but I am not sure.
>>
> 
> Did you mean, uImage_load() shouldn't do a decompression for ramdisk ?

Yes. If you look at u-boot source, you will notice that it will
decompress a kernel if it is gzip/bzip2/whatever compressed and ignore
the compression field in case of a ramdisk. I think you should behave
like u-boot does.

Sebastian

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