From: Dan Williams <dcbw@redhat•com>
To: "Bjørn Mork" <bjorn@mork•no>
Cc: netdev@vger•kernel.org, linux-usb@vger•kernel.org,
Enrico Mioso <mrkiko.rs@gmail•com>
Subject: Re: [PATCH net,stable] net: huawei_cdc_ncm: increase command buffer size
Date: Wed, 18 Jun 2014 09:03:17 -0500 [thread overview]
Message-ID: <1403100197.2266.14.camel@dcbw.local> (raw)
In-Reply-To: <1403094084-13588-1-git-send-email-bjorn@mork.no>
On Wed, 2014-06-18 at 14:21 +0200, Bjørn Mork wrote:
> Messages from the modem exceeding 256 bytes cause communication
> failure.
>
> The WDM protocol is strictly "read on demand", meaning that we only
> poll for unread data after receiving a notification from the modem.
> Since we have no way to know how much data the modem has to send,
> we must make sure that the buffer we provide is "big enough".
> Message truncation does not work. Truncated messages are left unread
> until the modem has another message to send. Which often won't
> happen until the userspace application has given up waiting for the
> final part of the last message, and therefore sends another command.
>
> With a proper CDC WDM function there is a descriptor telling us
> which buffer size the modem uses. But with this vendor specific
> implementation there is no known way to calculate the exact "big
> enough" number. It is an unknown property of the modem firmware.
> Experience has shown that 256 is too small. The discussion of
> this failure ended up concluding that 512 might be too small as
> well. So 1024 seems like a reasonable value for now.
>
> Fixes: 41c47d8cfd68 ("net: huawei_cdc_ncm: Introduce the huawei_cdc_ncm driver")
> Cc: Enrico Mioso <mrkiko.rs@gmail•com>
> Reported-by: Dan Williams <dcbw@redhat•com>
> Signed-off-by: Bjørn Mork <bjorn@mork•no>
Tested-by: Dan Williams <dcbw@redhat•com>
'<CR><LF>^SYSCFGEX:
("00","01","02","03","99"),((400380,"GSM900/GSM1800/WCDMA2100"),(6a80000,"GSM850/GSM1900/WCDMA850/AWS/WCDMA1900"),(3fffffff,"All bands")),(0-2),(0-4),((1081b,"LTE_B1/LTE_B2/LTE_B4/LTE_B5/LTE_B12/LTE_B17"),(7fffffffffffffff,"All bands"))<CR><LF><CR><LF>OK<CR><LF>'
I get the last "<LF>" now :)
> ---
>
> The problem is a showstopper for anyone hitting it, so I believe this
> fix should go into all maintained stable kernels with this driver.
> That is anything based on v3.13 or newer.
>
> Thanks,
> Bjørn
>
>
> drivers/net/usb/huawei_cdc_ncm.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/net/usb/huawei_cdc_ncm.c b/drivers/net/usb/huawei_cdc_ncm.c
> index f9822bc75425..5d95a13dbe2a 100644
> --- a/drivers/net/usb/huawei_cdc_ncm.c
> +++ b/drivers/net/usb/huawei_cdc_ncm.c
> @@ -84,12 +84,13 @@ static int huawei_cdc_ncm_bind(struct usbnet *usbnet_dev,
> ctx = drvstate->ctx;
>
> if (usbnet_dev->status)
> - /* CDC-WMC r1.1 requires wMaxCommand to be "at least 256
> - * decimal (0x100)"
> + /* The wMaxCommand buffer must be big enough to hold
> + * any message from the modem. Experience has shown
> + * that some replies are more than 256 bytes long
> */
> subdriver = usb_cdc_wdm_register(ctx->control,
> &usbnet_dev->status->desc,
> - 256, /* wMaxCommand */
> + 1024, /* wMaxCommand */
> huawei_cdc_ncm_wdm_manage_power);
> if (IS_ERR(subdriver)) {
> ret = PTR_ERR(subdriver);
next prev parent reply other threads:[~2014-06-18 14:03 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-06-18 12:21 [PATCH net,stable] net: huawei_cdc_ncm: increase command buffer size Bjørn Mork
[not found] ` <1403094084-13588-1-git-send-email-bjorn-yOkvZcmFvRU@public.gmane.org>
2014-06-18 13:41 ` Enrico Mioso
2014-06-18 13:45 ` Enrico Mioso
2014-06-18 14:03 ` Dan Williams [this message]
2014-06-18 16:32 ` Enrico Mioso
2014-06-18 17:55 ` Bjørn Mork
[not found] ` <1403100197.2266.14.camel-ZWpNTBV2bRGs1BDpvl8NfQ@public.gmane.org>
2014-06-19 7:48 ` Enrico Mioso
2014-06-22 2:34 ` David Miller
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1403100197.2266.14.camel@dcbw.local \
--to=dcbw@redhat$(echo .)com \
--cc=bjorn@mork$(echo .)no \
--cc=linux-usb@vger$(echo .)kernel.org \
--cc=mrkiko.rs@gmail$(echo .)com \
--cc=netdev@vger$(echo .)kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox