On Fri, 03 Dec 2021 15:52:48 +0100 Bjørn Mork wrote:
Lee Jones lee.jones@linaro.org writes:
diff --git a/drivers/net/usb/cdc_ncm.c b/drivers/net/usb/cdc_ncm.c index 24753a4da7e60..e303b522efb50 100644 --- a/drivers/net/usb/cdc_ncm.c +++ b/drivers/net/usb/cdc_ncm.c @@ -181,6 +181,8 @@ static u32 cdc_ncm_check_tx_max(struct usbnet *dev, u32 new_tx) min = ctx->max_datagram_size + ctx->max_ndp_size + sizeof(struct usb_cdc_ncm_nth32); max = min_t(u32, CDC_NCM_NTB_MAX_SIZE_TX, le32_to_cpu(ctx->ncm_parm.dwNtbOutMaxSize));
- if (max == 0)
max = CDC_NCM_NTB_MAX_SIZE_TX; /* dwNtbOutMaxSize not set *//* some devices set dwNtbOutMaxSize too low for the above default */ min = min(min, max);
I believe this is the best possible fix, considering the regressions anything stricter might cause.
We know of at least one MBIM device where dwNtbOutMaxSize is as low as 2048.
According to the MBIM spec, the minimum and default value for wMaxSegmentSize is also 2048. This implies that the calculated "min" value is at least 2076, which is why we need that odd looking
min = min(min, max);
So let's just fix this specific zero case without breaking the non-conforming devices.
Reviewed-by: Bjørn Mork bjorn@mork.no
Applied to net, thanks!