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Miller" , Matthias Brugger , John Crispin , Sean Wang , Mark Lee , Jakub Kicinski , Arnd Bergmann , Fabien Parent , Heiner Kallweit , Edwin Peer , devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mediatek@lists.infradead.org, Stephane Le Provost , Pedro Tsai , Andrew Perepech , Bartosz Golaszewski , clang-built-linux@googlegroups.com Subject: Re: [PATCH v5 06/11] net: ethernet: mtk-star-emac: new driver Message-ID: <20200527073150.GA3384158@ubuntu-s3-xlarge-x86> References: <20200522120700.838-1-brgl@bgdev.pl> <20200522120700.838-7-brgl@bgdev.pl> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200522120700.838-7-brgl@bgdev.pl> Sender: devicetree-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org On Fri, May 22, 2020 at 02:06:55PM +0200, Bartosz Golaszewski wrote: > diff --git a/drivers/net/ethernet/mediatek/mtk_star_emac.c b/drivers/net/ethernet/mediatek/mtk_star_emac.c > new file mode 100644 > index 000000000000..789c77af501f > --- /dev/null > +++ b/drivers/net/ethernet/mediatek/mtk_star_emac.c > @@ -0,0 +1,1678 @@ I've searched netdev and I cannot find any reports from others but this function introduces a clang warning: drivers/net/ethernet/mediatek/mtk_star_emac.c:1296:6: warning: variable 'new_dma_addr' is used uninitialized whenever 'if' condition is true [-Wsometimes-uninitialized] if (!new_skb) { ^~~~~~~~ drivers/net/ethernet/mediatek/mtk_star_emac.c:1321:23: note: uninitialized use occurs here desc_data.dma_addr = new_dma_addr; ^~~~~~~~~~~~ drivers/net/ethernet/mediatek/mtk_star_emac.c:1296:2: note: remove the 'if' if its condition is always false if (!new_skb) { ^~~~~~~~~~~~~~~ drivers/net/ethernet/mediatek/mtk_star_emac.c:1285:6: warning: variable 'new_dma_addr' is used uninitialized whenever 'if' condition is true [-Wsometimes-uninitialized] if ((desc_data.flags & MTK_STAR_DESC_BIT_RX_CRCE) || ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ drivers/net/ethernet/mediatek/mtk_star_emac.c:1321:23: note: uninitialized use occurs here desc_data.dma_addr = new_dma_addr; ^~~~~~~~~~~~ drivers/net/ethernet/mediatek/mtk_star_emac.c:1285:2: note: remove the 'if' if its condition is always false if ((desc_data.flags & MTK_STAR_DESC_BIT_RX_CRCE) || ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ drivers/net/ethernet/mediatek/mtk_star_emac.c:1285:6: warning: variable 'new_dma_addr' is used uninitialized whenever '||' condition is true [-Wsometimes-uninitialized] if ((desc_data.flags & MTK_STAR_DESC_BIT_RX_CRCE) || ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ drivers/net/ethernet/mediatek/mtk_star_emac.c:1321:23: note: uninitialized use occurs here desc_data.dma_addr = new_dma_addr; ^~~~~~~~~~~~ drivers/net/ethernet/mediatek/mtk_star_emac.c:1285:6: note: remove the '||' if its condition is always false if ((desc_data.flags & MTK_STAR_DESC_BIT_RX_CRCE) || ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ drivers/net/ethernet/mediatek/mtk_star_emac.c:1274:25: note: initialize the variable 'new_dma_addr' to silence this warning dma_addr_t new_dma_addr; ^ = 0 3 warnings generated. > +static int mtk_star_receive_packet(struct mtk_star_priv *priv) > +{ > + struct mtk_star_ring *ring = &priv->rx_ring; > + struct device *dev = mtk_star_get_dev(priv); > + struct mtk_star_ring_desc_data desc_data; > + struct net_device *ndev = priv->ndev; > + struct sk_buff *curr_skb, *new_skb; > + dma_addr_t new_dma_addr; Uninitialized here > + int ret; > + > + spin_lock(&priv->lock); > + ret = mtk_star_ring_pop_tail(ring, &desc_data); > + spin_unlock(&priv->lock); > + if (ret) > + return -1; > + > + curr_skb = desc_data.skb; > + > + if ((desc_data.flags & MTK_STAR_DESC_BIT_RX_CRCE) || > + (desc_data.flags & MTK_STAR_DESC_BIT_RX_OSIZE)) { > + /* Error packet -> drop and reuse skb. */ > + new_skb = curr_skb; > + goto push_new_skb; this goto > + } > + > + /* Prepare new skb before receiving the current one. Reuse the current > + * skb if we fail at any point. > + */ > + new_skb = mtk_star_alloc_skb(ndev); > + if (!new_skb) { > + ndev->stats.rx_dropped++; > + new_skb = curr_skb; > + goto push_new_skb; and this goto > + } > + > + new_dma_addr = mtk_star_dma_map_rx(priv, new_skb); > + if (dma_mapping_error(dev, new_dma_addr)) { > + ndev->stats.rx_dropped++; > + dev_kfree_skb(new_skb); > + new_skb = curr_skb; > + netdev_err(ndev, "DMA mapping error of RX descriptor\n"); > + goto push_new_skb; > + } > + > + /* We can't fail anymore at this point: it's safe to unmap the skb. */ > + mtk_star_dma_unmap_rx(priv, &desc_data); > + > + skb_put(desc_data.skb, desc_data.len); > + desc_data.skb->ip_summed = CHECKSUM_NONE; > + desc_data.skb->protocol = eth_type_trans(desc_data.skb, ndev); > + desc_data.skb->dev = ndev; > + netif_receive_skb(desc_data.skb); > + > +push_new_skb: > + desc_data.dma_addr = new_dma_addr; assign it uninitialized here. > + desc_data.len = skb_tailroom(new_skb); > + desc_data.skb = new_skb; > + > + spin_lock(&priv->lock); > + mtk_star_ring_push_head_rx(ring, &desc_data); > + spin_unlock(&priv->lock); > + > + return 0; > +} I don't know if there should be a new label that excludes that assignment for those particular gotos or if new_dma_addr should be initialized to something at the top. Please take a look at addressing this when you get a chance. Cheers, Nathan