[PATCH v11 01/29] net: recv(): return -EAGAIN instead of 0 when no cleanup is expected

[Simon Glass]

On Thu, 3 Oct 2024 at 09:23, Jerome Forissier
<jerome.forissier at linaro.org> wrote:
>
> Note: patch posted separately [0].
>
> [0] http://patchwork.ozlabs.org/project/uboot/patch/20240927142038.879037-1-jerome.forissier@linaro.org/
>
> 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 at 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 -EINVAL instead of 0 when no packet is
> available and the driver doesn't expect free_pkt() to be called
> subsequently.

Do you mean -EAGAIN ? Otherwise, it seems like this comment relates to
a different patch.

>
> [1] https://lists.denx.de/pipermail/u-boot/2024-August/562861.html
> [2] doc/develop/driver-model/ethernet.rst
>
> Signed-off-by: Jerome Forissier <jerome.forissier at linaro.org>
> ---
>  drivers/net/eepro100.c | 2 +-
>  drivers/net/rtl8139.c  | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
>

Reviewed-by: Simon Glass <sjg at chromium.org>


> diff --git a/drivers/net/eepro100.c b/drivers/net/eepro100.c
> index d18a8d577ca..f64dbb7d6a1 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 2e0afad089f..5f4b1e2d3a0 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.  */
> --
> 2.40.1
>