Re: [PATCH] mmc: omap_hsmmc: don't print uninitialized variables

Peter Ujfalusi
2016-01-26T14:52:40Z

On 01/25/2016 05:50 PM, Arnd Bergmann wrote:
> When DT based probing is used but the DMA request fails, the
> driver will print uninitialized stack data from the rx_req
> and tx_req variables, as indicated by this warning:
>
> drivers/mmc/host/omap_hsmmc.c: In function 'omap_hsmmc_probe':
> drivers/mmc/host/omap_hsmmc.c:2162:3: warning: 'rx_req' may be used uninitialized in this function [-Wmaybe-uninitialized]
> dev_err(mmc_dev(host->mmc), "unable to obtain RX DMA engine channel %u\n", rx_req);
>
> This restructures the function to separate the simple DT probe
> from the more complex platform data code path, and only
> prints the information that is actually available and
> needed in case of an error, which makes it nicer to read
> and avoids the warning.
>
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
> drivers/mmc/host/omap_hsmmc.c | 48 +++++++++++++++++++++----------------------
> 1 file changed, 23 insertions(+), 25 deletions(-)
>
> diff --git a/drivers/mmc/host/omap_hsmmc.c b/drivers/mmc/host/omap_hsmmc.c
> index b6639ea0bf18..e06b1881b6a1 100644
> --- a/drivers/mmc/host/omap_hsmmc.c
> +++ b/drivers/mmc/host/omap_hsmmc.c
> @@ -2002,8 +2002,6 @@ static int omap_hsmmc_probe(struct platform_device *pdev)
> struct resource *res;
> int ret, irq;
> const struct of_device_id *match;
> - dma_cap_mask_t mask;
> - unsigned tx_req, rx_req;
> const struct omap_mmc_of_data *data;
> void __iomem *base;
>
> @@ -2133,7 +2131,17 @@ static int omap_hsmmc_probe(struct platform_device *pdev)
>
> omap_hsmmc_conf_bus_power(host);
>
> - if (!pdev->dev.of_node) {
> + host->tx_chan = dma_request_slave_channel(&pdev->dev, "tx");
> + host->rx_chan = dma_request_slave_channel(&pdev->dev, "rx");
> + if (!host->tx_chan || !host->rx_chan) {

While it is really unlikely that we are failing to get only one of the
channels... It means anyway that the omap_hsmmc is not usable, but we will
still try to get via legacy mode and there is a chance that we might get some
channel.

Too bad that I can not send the conversion to dma_request_chan() yet due to
missing things in arch...

It might be simpler to just remove the printout of the rx/tx_req from the
dev_err() when reporting failed channel requests...

> + dma_cap_mask_t mask;
> + unsigned tx_req, rx_req;
> +
> + dev_err(mmc_dev(host->mmc), "falling back to manual DMA configuration\n");
> +
> + dma_cap_zero(mask);
> + dma_cap_set(DMA_SLAVE, mask);
> +
> res = platform_get_resource_byname(pdev, IORESOURCE_DMA, "tx");
> if (!res) {
> dev_err(mmc_dev(host->mmc), "cannot get DMA TX channel\n");
> @@ -2141,6 +2149,12 @@ static int omap_hsmmc_probe(struct platform_device *pdev)
> goto err_irq;
> }
> tx_req = res->start;
> + host->tx_chan = dma_request_channel(mask, omap_dma_filter_fn, &tx_req);
> + if (!host->rx_chan) {
> + dev_err(mmc_dev(host->mmc), "unable to obtain TX DMA engine channel %u\n", tx_req);
> + ret = -ENXIO;
> + goto err_irq;
> + }
>
> res = platform_get_resource_byname(pdev, IORESOURCE_DMA, "rx");
> if (!res) {
> @@ -2149,29 +2163,13 @@ static int omap_hsmmc_probe(struct platform_device *pdev)
> goto err_irq;
> }
> rx_req = res->start;
> - }
> -
> - dma_cap_zero(mask);
> - dma_cap_set(DMA_SLAVE, mask);
> -
> - host->rx_chan =
> - dma_request_slave_channel_compat(mask, omap_dma_filter_fn,
> - &rx_req, &pdev->dev, "rx");
> + host->tx_chan = dma_request_channel(mask, omap_dma_filter_fn, &rx_req);
>
> - if (!host->rx_chan) {
> - dev_err(mmc_dev(host->mmc), "unable to obtain RX DMA engine channel %u\n", rx_req);
> - ret = -ENXIO;
> - goto err_irq;
> - }
> -
> - host->tx_chan =
> - dma_request_slave_channel_compat(mask, omap_dma_filter_fn,
> - &tx_req, &pdev->dev, "tx");
> -
> - if (!host->tx_chan) {
> - dev_err(mmc_dev(host->mmc), "unable to obtain TX DMA engine channel %u\n", tx_req);
> - ret = -ENXIO;
> - goto err_irq;
> + if (!host->tx_chan) {
> + dev_err(mmc_dev(host->mmc), "unable to obtain RX DMA engine channel %u\n", rx_req);
> + ret = -ENXIO;
> + goto err_irq;
> + }
> }
>
> /* Request IRQ for MMC operations */
>

--
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