From 63150710e34aa9d5d7c45e142e70016b31af2c04 Mon Sep 17 00:00:00 2001 From: Jerome Forissier Date: Wed, 9 Oct 2024 11:42:08 +0200 Subject: [PATCH] net: recv(): return -EAGAIN instead of 0 when no cleanup is expected Some drivers do not behave properly when free_pkt() is called with a length of zero. It is an issue I observed when developing the lwIP series [1] (see "QEMU CI tests for r2dplus_i82557c, r2dplus_rtl8139" in the change log) and which I fixed incorrectly by not calling free_pkt() when recv() returns 0. That turned out to be wrong for two reasons: 1. The DM documentation [2] clearly requires it: "The **recv** function polls for availability of a new packet. [...] If there is an error [...], return 0 if you require the packet to be cleaned up normally, or a negative error code otherwise (cleanup not necessary or already done). If **free_pkt** is defined, U-Boot will call it after a received packet has been processed [...]. free_pkt() will be called after recv(), for the same packet [...]" 2. The imx8mp_evk platform will fail with OOM errors if free_pkt() is not called after recv() returns 0: u-boot=> tftp 192.168.0.16:50M Using ethernet@30be0000 device TFTP from server 192.168.0.16; our IP address is 192.168.0.48 Filename '50M'. Load address: 0x40480000 Loading: #######################fecmxc_recv: error allocating packetp fecmxc_recv: error allocating packetp fecmxc_recv: error allocating packetp ... Therefore, make recv() return -EAGAIN instead of 0 when no packet is available and the driver doesn't expect free_pkt() to be called subsequently. [1] https://lists.denx.de/pipermail/u-boot/2024-August/562861.html [2] doc/develop/driver-model/ethernet.rst Signed-off-by: Jerome Forissier Reviewed-by: Simon Glass --- drivers/net/eepro100.c | 2 +- drivers/net/rtl8139.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/net/eepro100.c b/drivers/net/eepro100.c index d18a8d577c..f64dbb7d6a 100644 --- a/drivers/net/eepro100.c +++ b/drivers/net/eepro100.c @@ -678,7 +678,7 @@ static int eepro100_recv_common(struct eepro100_priv *priv, uchar **packetp) status = le16_to_cpu(desc->status); if (!(status & RFD_STATUS_C)) - return 0; + return -EAGAIN; /* Valid frame status. */ if (status & RFD_STATUS_OK) { diff --git a/drivers/net/rtl8139.c b/drivers/net/rtl8139.c index 2e0afad089..5f4b1e2d3a 100644 --- a/drivers/net/rtl8139.c +++ b/drivers/net/rtl8139.c @@ -433,7 +433,7 @@ static int rtl8139_recv_common(struct rtl8139_priv *priv, unsigned char *rxdata, int length = 0; if (inb(priv->ioaddr + RTL_REG_CHIPCMD) & RTL_REG_CHIPCMD_RXBUFEMPTY) - return 0; + return -EAGAIN; priv->rxstatus = inw(priv->ioaddr + RTL_REG_INTRSTATUS); /* See below for the rest of the interrupt acknowledges. */ -- 2.39.5