From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arnd Bergmann Date: Mon, 07 Nov 2016 13:50:27 +0000 Subject: Re: [PATCH] serial: sirf: Simplify a test Message-Id: <2916662.De1FDumaQl@wuerfel> List-Id: References: <20161101070333.12255-1-christophe.jaillet@wanadoo.fr> In-Reply-To: <20161101070333.12255-1-christophe.jaillet@wanadoo.fr> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-arm-kernel@lists.infradead.org On Tuesday, November 1, 2016 8:03:33 AM CET Christophe JAILLET wrote: > 'dmaengine_prep_dma_cyclic()' does not return an error pointer, so the test > can be simplified to be more consistent. > > Signed-off-by: Christophe JAILLET The change looks correct in principle. It would be good to automate looking for other instances of this bug. How did you find it? Do you have e.g. a coccinelle script or did you just stumble over the issue by accident? There is one problem with your patch: > drivers/tty/serial/sirfsoc_uart.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/tty/serial/sirfsoc_uart.c b/drivers/tty/serial/sirfsoc_uart.c > index b186c9c4f850..666ca3156961 100644 > --- a/drivers/tty/serial/sirfsoc_uart.c > +++ b/drivers/tty/serial/sirfsoc_uart.c > @@ -609,7 +609,7 @@ static void sirfsoc_uart_start_next_rx_dma(struct uart_port *port) > sirfport->rx_dma_items.dma_addr, SIRFSOC_RX_DMA_BUF_SIZE, > SIRFSOC_RX_DMA_BUF_SIZE / 2, > DMA_DEV_TO_MEM, DMA_PREP_INTERRUPT); > - if (IS_ERR_OR_NULL(sirfport->rx_dma_items.desc)) { > + if (!sirfport->rx_dma_items.desc) { > dev_err(port->dev, "DMA slave single fail\n"); > return; > } The serial driver is for the sirf platform, which uses the sirf-dma dmaengine driver, and that particular driver has an incorrect dma_prep_cyclic implementation, so I think we also need this fix: diff --git a/drivers/dma/sirf-dma.c b/drivers/dma/sirf-dma.c index 8f62edad51be..220c611c89ae 100644 --- a/drivers/dma/sirf-dma.c +++ b/drivers/dma/sirf-dma.c @@ -775,7 +775,7 @@ sirfsoc_dma_prep_cyclic(struct dma_chan *chan, dma_addr_t addr, * BUFB */ if (buf_len != 2 * period_len) - return ERR_PTR(-EINVAL); + return NULL; /* Get free descriptor */ spin_lock_irqsave(&schan->lock, iflags); Arnd