On 12/05/15 09:39, Alexandre Courbot wrote:
> On Tue, May 5, 2015 at 11:17 PM, Jon Hunter <jonathanh@xxxxxxxxxx> wrote:
>> Function tegra_uart_dma_channel_allocate() does not check that
>> dma_map_single() mapped the DMA buffer correctly. Add a check for this
>> and appropriate error handling.
>>
>> Furthermore, if dmaengine_slave_config() (called by
>> tegra_uart_dma_channel_allocate()) fails, then memory allocated/mapped
>> is not freed/unmapped. Therefore, call tegra_uart_dma_channel_free()
>> instead of just dma_release_channel() if dmaengine_slave_config() fails.
>>
>> Signed-off-by: Jon Hunter <jonathanh@xxxxxxxxxx>
>> ---
>> drivers/tty/serial/serial-tegra.c | 51 +++++++++++++++++++++------------------
>> 1 file changed, 28 insertions(+), 23 deletions(-)
>>
>> diff --git a/drivers/tty/serial/serial-tegra.c b/drivers/tty/serial/serial-tegra.c
>> index 96378da9aefc..3b63f103f0c9 100644
>> --- a/drivers/tty/serial/serial-tegra.c
>> +++ b/drivers/tty/serial/serial-tegra.c
>> @@ -949,6 +949,28 @@ static int tegra_uart_hw_init(struct tegra_uart_port *tup)
>> return 0;
>> }
>>
>> +static void tegra_uart_dma_channel_free(struct tegra_uart_port *tup,
>> + bool dma_to_memory)
>> +{
>> + if (dma_to_memory) {
>> + dmaengine_terminate_all(tup->rx_dma_chan);
>> + dma_release_channel(tup->rx_dma_chan);
>> + dma_free_coherent(tup->uport.dev, TEGRA_UART_RX_DMA_BUFFER_SIZE,
>> + tup->rx_dma_buf_virt, tup->rx_dma_buf_phys);
>> + tup->rx_dma_chan = NULL;
>> + tup->rx_dma_buf_phys = 0;
>> + tup->rx_dma_buf_virt = NULL;
>> + } else {
>> + dmaengine_terminate_all(tup->tx_dma_chan);
>> + dma_release_channel(tup->tx_dma_chan);
>> + dma_unmap_single(tup->uport.dev, tup->tx_dma_buf_phys,
>> + UART_XMIT_SIZE, DMA_TO_DEVICE);
>> + tup->tx_dma_chan = NULL;
>> + tup->tx_dma_buf_phys = 0;
>> + tup->tx_dma_buf_virt = NULL;
>> + }
>> +}
>> +
>> static int tegra_uart_dma_channel_allocate(struct tegra_uart_port *tup,
>> bool dma_to_memory)
>> {
>> @@ -981,6 +1003,11 @@ static int tegra_uart_dma_channel_allocate(struct tegra_uart_port *tup,
>> dma_phys = dma_map_single(tup->uport.dev,
>> tup->uport.state->xmit.buf, UART_XMIT_SIZE,
>> DMA_TO_DEVICE);
>> + if (dma_mapping_error(tup->uport.dev, dma_phys)) {
>> + dev_err(tup->uport.dev, "dma_map_single tx failed\n");
>> + dma_release_channel(dma_chan);
>> + return -ENOMEM;
>
> Is -ENOMEM the error code we want to return here?
I think that it is appropriate as we are unable to map the memory we are
requesting. I did look at a few other drivers and several return -ENOMEM
here. I saw others return -EFAULT, but given this is memory related,
seems ok, unless you have a better suggestion.
> IIUC dma_buf will be leaked if an error occurs here because it has not
> been assigned to your structure and will therefore be ignored when
> tegra_uart_dma_channel_free() is called.
In the original code, if dmaengine_slave_config() failed, then yes there
would be a memory leak. That should no longer be the case.
> Since we have a "scrub" label at the end of this function, I think I'd
> also prefer if this block and the one before could jump to error
> labels as well for consistency.
Yes I see. I wondered if it would be better to just get rid of the
"scrub" label since it is only used in one place instead?
By the way, I got a notification from Greg that these are now queued in
his tty-testing branch [1]. Assuming these are ok, may be I could fix
that up in a follow-up patch?
> Otherwise, pretty nice series, comprehensive and easy to read.
Thanks!
Jon
[1]
http://git.kernel.org/cgit/linux/kernel/git/gregkh/tty.git/log/?h=tty-testing
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