modules/gralloc/mapper.cpp

/*
 * Copyright (C) 2008 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include <errno.h>
#include <limits.h>
#include <pthread.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>

#include <cutils/atomic.h>
#include <log/log.h>

#include <hardware/hardware.h>
#include <hardware/gralloc.h>

#include "gralloc_priv.h"


/*****************************************************************************/

static int gralloc_map(gralloc_module_t const* /*module*/,
        buffer_handle_t handle,
        void** vaddr)
{
    private_handle_t* hnd = (private_handle_t*)handle;
    if (!(hnd->flags & private_handle_t::PRIV_FLAGS_FRAMEBUFFER)) {
        size_t size = hnd->size;
        void* mappedAddress = mmap(0, size,
                PROT_READ|PROT_WRITE, MAP_SHARED, hnd->fd, 0);
        if (mappedAddress == MAP_FAILED) {
            ALOGE("Could not mmap %s", strerror(errno));
            return -errno;
        }
        hnd->base = uintptr_t(mappedAddress) + hnd->offset;
        //ALOGD("gralloc_map() succeeded fd=%d, off=%d, size=%d, vaddr=%p",
        //        hnd->fd, hnd->offset, hnd->size, mappedAddress);
    }
    *vaddr = (void*)hnd->base;
    return 0;
}

static int gralloc_unmap(gralloc_module_t const* /*module*/,
        buffer_handle_t handle)
{
    private_handle_t* hnd = (private_handle_t*)handle;
    if (!(hnd->flags & private_handle_t::PRIV_FLAGS_FRAMEBUFFER)) {
        void* base = (void*)hnd->base;
        size_t size = hnd->size;
        //ALOGD("unmapping from %p, size=%d", base, size);
        if (munmap(base, size) < 0) {
            ALOGE("Could not unmap %s", strerror(errno));
        }
    }
    hnd->base = 0;
    return 0;
}

/*****************************************************************************/

int gralloc_register_buffer(gralloc_module_t const* module,
        buffer_handle_t handle)
{
    if (private_handle_t::validate(handle) < 0)
        return -EINVAL;

    // *** WARNING WARNING WARNING ***
    //
    // If a buffer handle is passed from the process that allocated it to a
    // different process, and then back to the allocator process, we will
    // create a second mapping of the buffer. If the process reads and writes
    // through both mappings, normal memory ordering guarantees may be
    // violated, depending on the processor cache implementation*.
    //
    // If you are deriving a new gralloc implementation from this code, don't
    // do this. A "real" gralloc should provide a single reference-counted
    // mapping for each buffer in a process.
    //
    // In the current system, there is one case that needs a buffer to be
    // registered in the same process that allocated it. The SurfaceFlinger
    // process acts as the IGraphicBufferAlloc Binder provider, so all gralloc
    // allocations happen in its process. After returning the buffer handle to
    // the IGraphicBufferAlloc client, SurfaceFlinger free's its handle to the
    // buffer (unmapping it from the SurfaceFlinger process). If
    // SurfaceFlinger later acts as the producer end of the buffer queue the
    // buffer belongs to, it will get a new handle to the buffer in response
    // to IGraphicBufferProducer::requestBuffer(). Like any buffer handle
    // received through Binder, the SurfaceFlinger process will register it.
    // Since it already freed its original handle, it will only end up with
    // one mapping to the buffer and there will be no problem.
    //
    // Currently SurfaceFlinger only acts as a buffer producer for a remote
    // consumer when taking screenshots and when using virtual displays.
    //
    // Eventually, each application should be allowed to make its own gralloc
    // allocations, solving the problem. Also, this ashmem-based gralloc
    // should go away, replaced with a real ion-based gralloc.
    //
    // * Specifically, associative virtually-indexed caches are likely to have
    //   problems. Most modern L1 caches fit that description.

    private_handle_t* hnd = (private_handle_t*)handle;
    ALOGD_IF(hnd->pid == getpid(),
            "Registering a buffer in the process that created it. "
            "This may cause memory ordering problems.");

    void *vaddr;
    return gralloc_map(module, handle, &vaddr);
}

int gralloc_unregister_buffer(gralloc_module_t const* module,
        buffer_handle_t handle)
{
    if (private_handle_t::validate(handle) < 0)
        return -EINVAL;

    private_handle_t* hnd = (private_handle_t*)handle;
    if (hnd->base)
        gralloc_unmap(module, handle);

    return 0;
}

int mapBuffer(gralloc_module_t const* module,
        private_handle_t* hnd)
{
    void* vaddr;
    return gralloc_map(module, hnd, &vaddr);
}

int terminateBuffer(gralloc_module_t const* module,
        private_handle_t* hnd)
{
    if (hnd->base) {
        // this buffer was mapped, unmap it now
        gralloc_unmap(module, hnd);
    }

    return 0;
}

int gralloc_lock(gralloc_module_t const* /*module*/,
        buffer_handle_t handle, int /*usage*/,
        int /*l*/, int /*t*/, int /*w*/, int /*h*/,
        void** vaddr)
{
    // this is called when a buffer is being locked for software
    // access. in thin implementation we have nothing to do since
    // not synchronization with the h/w is needed.
    // typically this is used to wait for the h/w to finish with
    // this buffer if relevant. the data cache may need to be
    // flushed or invalidated depending on the usage bits and the
    // hardware.

    if (private_handle_t::validate(handle) < 0)
        return -EINVAL;

    private_handle_t* hnd = (private_handle_t*)handle;
    *vaddr = (void*)hnd->base;
    return 0;
}

int gralloc_unlock(gralloc_module_t const* /*module*/,
        buffer_handle_t handle)
{
    // we're done with a software buffer. nothing to do in this
    // implementation. typically this is used to flush the data cache.

    if (private_handle_t::validate(handle) < 0)
        return -EINVAL;
    return 0;
}