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Wed, 01 Apr 2020 13:34:28 +0200 Received: from euls16034.sgp.st.com (euls16034.sgp.st.com [10.75.44.20]) by beta.dmz-eu.st.com (STMicroelectronics) with ESMTP id A7BAD10002A; Wed, 1 Apr 2020 13:34:24 +0200 (CEST) Received: from Webmail-eu.st.com (sfhdag3node1.st.com [10.75.127.7]) by euls16034.sgp.st.com (STMicroelectronics) with ESMTP id 8FFA92A620D; Wed, 1 Apr 2020 13:34:24 +0200 (CEST) Received: from lmecxl0889.tpe.st.com (10.75.127.51) by SFHDAG3NODE1.st.com (10.75.127.7) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Wed, 1 Apr 2020 13:34:22 +0200 Subject: Re: [PATCH v7 1/2] rpmsg: core: add API to get MTU To: Jiri Slaby , Ohad Ben-Cohen , Bjorn Andersson , Greg Kroah-Hartman , , , Mathieu Poirier CC: Suman Anna , Fabien DESSENNE , , xiang xiao References: <20200324170407.16470-1-arnaud.pouliquen@st.com> <20200324170407.16470-2-arnaud.pouliquen@st.com> <356fe539-6ec4-6000-1f68-23404fc5d373@suse.com> <9f302a19-e684-ffff-823a-02af7f90403c@suse.cz> From: Arnaud POULIQUEN Message-ID: <1edf98cf-dfb6-0e66-a58d-abba5d2a65c4@st.com> Date: Wed, 1 Apr 2020 13:34:19 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: <9f302a19-e684-ffff-823a-02af7f90403c@suse.cz> Content-Type: text/plain; charset="iso-8859-2" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.75.127.51] X-ClientProxiedBy: SFHDAG3NODE2.st.com (10.75.127.8) To SFHDAG3NODE1.st.com (10.75.127.7) X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.138,18.0.676 definitions=2020-04-01_01:2020-03-31,2020-03-31 signatures=0 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 4/1/20 8:29 AM, Jiri Slaby wrote: > On 01. 04. 20, 8:28, Jiri Slaby wrote: >> On 24. 03. 20, 18:04, Arnaud Pouliquen wrote: >>> Return the rpmsg buffer MTU for sending message, so rpmsg users >>> can split a long message in several sub rpmsg buffers. >>> >>> Signed-off-by: Arnaud Pouliquen >>> Acked-by: Suman Anna >>> --- >>> drivers/rpmsg/rpmsg_core.c | 21 +++++++++++++++++++++ >>> drivers/rpmsg/rpmsg_internal.h | 2 ++ >>> drivers/rpmsg/virtio_rpmsg_bus.c | 10 ++++++++++ >>> include/linux/rpmsg.h | 10 ++++++++++ >>> 4 files changed, 43 insertions(+) >>> >>> diff --git a/drivers/rpmsg/rpmsg_core.c b/drivers/rpmsg/rpmsg_core.c >>> index e330ec4dfc33..a6ef54c4779a 100644 >>> --- a/drivers/rpmsg/rpmsg_core.c >>> +++ b/drivers/rpmsg/rpmsg_core.c >>> @@ -283,6 +283,27 @@ int rpmsg_trysend_offchannel(struct rpmsg_endpoint *ept, u32 src, u32 dst, >>> } >>> EXPORT_SYMBOL(rpmsg_trysend_offchannel); >>> >>> +/** >>> + * rpmsg_get_mtu() - get maximum transmission buffer size for sending message. >>> + * @ept: the rpmsg endpoint >>> + * >>> + * This function returns maximum buffer size available for a single message. >>> + * >>> + * Return: the maximum transmission size on success and an appropriate error >>> + * value on failure. >>> + */ >>> + >>> +ssize_t rpmsg_get_mtu(struct rpmsg_endpoint *ept) >>> +{ >>> + if (WARN_ON(!ept)) >>> + return -EINVAL; >>> + if (!ept->ops->get_mtu) >>> + return -ENOTSUPP; >> >> Hmm, I don't think all callers of tty_write_room() handle negative values... >> >> But some drivers also return negative values. There is some work to be >> done, adding to TODO. >> >> For the time being, I suggest returning 0 instead. > > Or better, convert the negative to 0 in rpmsg_tty_write_room for now. > >> thanks,-- Right, seems that a negative return of tty_write_room seems not always handled so i will force to 0 in rpmsg_tty in case of error returned. I will also add a comment in code that explain the context. Thanks, Arnaud