Hi Laurent,
On 05/08/2012 02:44 PM, Laurent Pinchart wrote:
> Hi Subash,
>
> On Monday 07 May 2012 20:08:25 Subash Patel wrote:
>> Hello Thomasz, Laurent,
>>
>> I found an issue in the function vb2_dc_pages_to_sgt() below. I saw that
>> during the attach, the size of the SGT and size requested mis-matched
>> (by atleast 8k bytes). Hence I made a small correction to the code as
>> below. I could then attach the importer properly.
>
> Thank you for the report.
>
> Could you print the content of the sglist (number of chunks and size of each
> chunk) before and after your modifications, as well as the values of n_pages,
> offset and size ?
I will put back all the printk's and generate this. As of now, my setup
has changed and will do this when I get sometime.
>
>> On 04/20/2012 08:15 PM, Tomasz Stanislawski wrote:
>
> [snip]
>
>>> +static struct sg_table *vb2_dc_pages_to_sgt(struct page **pages,
>>> + unsigned int n_pages, unsigned long offset, unsigned long size)
>>> +{
>>> + struct sg_table *sgt;
>>> + unsigned int chunks;
>>> + unsigned int i;
>>> + unsigned int cur_page;
>>> + int ret;
>>> + struct scatterlist *s;
>>> +
>>> + sgt = kzalloc(sizeof *sgt, GFP_KERNEL);
>>> + if (!sgt)
>>> + return ERR_PTR(-ENOMEM);
>>> +
>>> + /* compute number of chunks */
>>> + chunks = 1;
>>> + for (i = 1; i< n_pages; ++i)
>>> + if (pages[i] != pages[i - 1] + 1)
>>> + ++chunks;
>>> +
>>> + ret = sg_alloc_table(sgt, chunks, GFP_KERNEL);
>>> + if (ret) {
>>> + kfree(sgt);
>>> + return ERR_PTR(-ENOMEM);
>>> + }
>>> +
>>> + /* merging chunks and putting them into the scatterlist */
>>> + cur_page = 0;
>>> + for_each_sg(sgt->sgl, s, sgt->orig_nents, i) {
>>> + unsigned long chunk_size;
>>> + unsigned int j;
>>
>> size = PAGE_SIZE;
>>
>>> +
>>> + for (j = cur_page + 1; j< n_pages; ++j)
>>
>> for (j = cur_page + 1; j< n_pages; ++j) {
>>
>>> + if (pages[j] != pages[j - 1] + 1)
>>> + break;
>>
>> size += PAGE
>> }
>>
>>> +
>>> + chunk_size = ((j - cur_page)<< PAGE_SHIFT) - offset;
>>> + sg_set_page(s, pages[cur_page], min(size, chunk_size), offset);
>>
>> [DELETE] size -= chunk_size;
>>
>>> + offset = 0;
>>> + cur_page = j;
>>> + }
>>> +
>>> + return sgt;
>>> +}
>
Regards,
Subash
