Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
From:   Je Yen Tam <je.yen.tam@ni.com>
To:     Greg KH <gregkh@linuxfoundation.org>
CC:     "linux-serial@vger.kernel.org" <linux-serial@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Thread-Topic: [EXTERNAL] Re: [PATCH] Revert "serial/8250: Add support for
 NI-Serial PXI/PXIe+485 devices"
Thread-Index: AQHVpNFY41vflLOwrUyBaS1l7dEVIqeelquAgAACTOA=
Date:   Wed, 27 Nov 2019 07:23:39 +0000
Message-ID: <MN2PR04MB5920DA1BBA0AF9D07E48EAC1B7440@MN2PR04MB5920.namprd04.prod.outlook.com>
References: <20191127031751.9082-1-je.yen.tam@ni.com>
 <20191127065903.GA1725222@kroah.com>
In-Reply-To: <20191127065903.GA1725222@kroah.com>
Accept-Language: en-US
Content-Language: en-US
received-spf: None (protection.outlook.com: ni.com does not designate
 permitted sender hosts)
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0
X-MS-Exchange-CrossTenant-Network-Message-Id: 3d3236a9-0e11-4ec1-d531-08d7730ab974
X-MS-Exchange-CrossTenant-originalarrivaltime: 27 Nov 2019 07:23:39.4073
 (UTC)
X-MS-Exchange-CrossTenant-fromentityheader: Hosted
X-MS-Exchange-CrossTenant-id: 87ba1f9a-44cd-43a6-b008-6fdb45a5204e
X-MS-Exchange-CrossTenant-mailboxtype: HOSTED
X-MS-Exchange-CrossTenant-userprincipalname: rqsp6RXoRwQcezRrWpzMnOZhNZ8yOJOr7lCXfh0zOHbI2DP02UnYETnY8WCIz1mDJT/6LEzWqrdZ0qI709OpLg==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: MN2PR04MB6254
Subject: RE: Re: [PATCH] Revert "serial/8250: Add support for NI-Serial PXI/PXIe+485
 devices"
X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.95,18.0.572
 definitions=2019-11-27_01:2019-11-27,2019-11-27 signatures=0
X-Proofpoint-Spam-Details: rule=inbound_policy_notspam policy=inbound_policy score=30 clxscore=1015
 malwarescore=0 impostorscore=0 mlxscore=0 phishscore=0 suspectscore=0
 lowpriorityscore=0 priorityscore=1501 bulkscore=0 mlxlogscore=999
 spamscore=0 adultscore=0 classifier=spam adjust=30 reason=mlx scancount=1
 engine=8.12.0-1910280000 definitions=main-1911270059
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

> Subject: [EXTERNAL] Re: [PATCH] Revert "serial/8250: Add support for NI-S=
erial
> PXI/PXIe+485 devices"
>=20
> On Wed, Nov 27, 2019 at 11:17:51AM +0800, Je Yen Tam wrote:
> > This reverts commit fdc2de87124f5183a98ea7eced1f76dbdba22951 which is
> > commit 225607f75454 ("serial/8250: Add support for NI-Serial PXI/PXIe+4=
85
> devices").
>=20
> That sentance does not make sense.  fdc2de87124f ("serial/8250: Add suppo=
rt for
> NI-Serial PXI/PXIe+485 devices") is in the 5.4 kernel tree, where did the=
 commit id
> "225607f75454" come from?  I don't see it anywhere in Linus's tree.

Overlooked the commit 225607f75454 which only visible to my own branch, wil=
l=20
remove it, sorry for the confusion.

> > The upstream introduced a breakage on NI-Serial PXI(e)-RS485 devices,
> > RS-232 variants have no issue. The Linux system can enumerate the
> > Serial
> > PXI(e)-RS485 devices, but it broke the R/W operation on the ports.
>=20
> I can not parse this paragraph either, what do you mean by "The upstream"=
?

"The upstream" actually means the commit fdc2de87124f. To be more specific,=
 will
rephrase it to "The commit fdc2de87124f".

> > However, the implementation is working on the NI internal Linux RT
> > kernel but it does not work in the Linux main tree kernel. This is
> > only affecting NI products, specifically the RS-485 variants.
> > Reverting the upstream until a proper implementation that can apply to
> > both NI internal Linux kernel and Linux mainline kernel is figured out.
>=20
> So this patch really does not work at all?  Can't you just find a simple =
fix to go on top
> of it to resolve the issue?  You really want it all ripped out for 5.5 an=
d 5.4.y?

It does work in NI Linux kernel but not in generic Linux kernel from the ma=
in tree, NI's
Serial team's decision is to have a cleaner implementation so decided to ri=
p out all of it
for 5.5 and 5.4.y to prevent unexpected breakage.

> thanks,
>=20
> greg k-h