drm_buffer.c

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/**************************************************************************
 *
 * Copyright 2010 Pauli Nieminen.
 * All Rights Reserved.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sub license, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice (including the
 * next paragraph) shall be included in all copies or substantial portions
 * of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
 * THE COPYRIGHT HOLDERS, AUTHORS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM,
 * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
 * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
 * USE OR OTHER DEALINGS IN THE SOFTWARE.
 *
 *
 **************************************************************************/
/*
 * Multipart buffer for coping data which is larger than the page size.
 *
 * Authors:
 * Pauli Nieminen <suokkos-at-gmail-dot-com>
 */

#include <linux/export.h>
#include <drm/drm_buffer.h>

int drm_buffer_alloc(struct drm_buffer **buf, int size)
{
    int nr_pages = size / PAGE_SIZE + 1;
    int idx;

    /* Allocating pointer table to end of structure makes drm_buffer
     * variable sized */
    *buf = kzalloc(sizeof(struct drm_buffer) + nr_pages*sizeof(char *),
            GFP_KERNEL);

    if (*buf == NULL) {
        DRM_ERROR("Failed to allocate drm buffer object to hold"
                " %d bytes in %d pages.\n",
                size, nr_pages);
        return -ENOMEM;
    }

    (*buf)->size = size;

    for (idx = 0; idx < nr_pages; ++idx) {

        (*buf)->data[idx] =
            kmalloc(min(PAGE_SIZE, size - idx * PAGE_SIZE),
                GFP_KERNEL);


        if ((*buf)->data[idx] == NULL) {
            DRM_ERROR("Failed to allocate %dth page for drm"
                    " buffer with %d bytes and %d pages.\n",
                    idx + 1, size, nr_pages);
            goto error_out;
        }

    }

    return 0;

error_out:

    /* Only last element can be null pointer so check for it first. */
    if ((*buf)->data[idx])
        kfree((*buf)->data[idx]);

    for (--idx; idx >= 0; --idx)
        kfree((*buf)->data[idx]);

    kfree(*buf);
    return -ENOMEM;
}
EXPORT_SYMBOL(drm_buffer_alloc);

int drm_buffer_copy_from_user(struct drm_buffer *buf,
                  void __user *user_data, int size)
{
    int nr_pages = size / PAGE_SIZE + 1;
    int idx;

    if (size > buf->size) {
        DRM_ERROR("Requesting to copy %d bytes to a drm buffer with"
                " %d bytes space\n",
                size, buf->size);
        return -EFAULT;
    }

    for (idx = 0; idx < nr_pages; ++idx) {

        if (DRM_COPY_FROM_USER(buf->data[idx],
            user_data + idx * PAGE_SIZE,
            min(PAGE_SIZE, size - idx * PAGE_SIZE))) {
            DRM_ERROR("Failed to copy user data (%p) to drm buffer"
                    " (%p) %dth page.\n",
                    user_data, buf, idx);
            return -EFAULT;

        }
    }
    buf->iterator = 0;
    return 0;
}
EXPORT_SYMBOL(drm_buffer_copy_from_user);

void drm_buffer_free(struct drm_buffer *buf)
{

    if (buf != NULL) {

        int nr_pages = buf->size / PAGE_SIZE + 1;
        int idx;
        for (idx = 0; idx < nr_pages; ++idx)
            kfree(buf->data[idx]);

        kfree(buf);
    }
}
EXPORT_SYMBOL(drm_buffer_free);

void *drm_buffer_read_object(struct drm_buffer *buf,
        int objsize, void *stack_obj)
{
    int idx = drm_buffer_index(buf);
    int page = drm_buffer_page(buf);
    void *obj = NULL;

    if (idx + objsize <= PAGE_SIZE) {
        obj = &buf->data[page][idx];
    } else {
        /* The object is split which forces copy to temporary object.*/
        int beginsz = PAGE_SIZE - idx;
        memcpy(stack_obj, &buf->data[page][idx], beginsz);

        memcpy(stack_obj + beginsz, &buf->data[page + 1][0],
                objsize - beginsz);

        obj = stack_obj;
    }

    drm_buffer_advance(buf, objsize);
    return obj;
}
EXPORT_SYMBOL(drm_buffer_read_object);