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To: "Matwey V. Kornilov" , Andy Shevchenko Cc: Greg Kroah-Hartman , Jiri Slaby , Matthias Brugger , Kees Cook , Allen Pais , Sean Young , "open list:SERIAL DRIVERS" , open list References: <20180606094942.71190-1-giulio.benetti@micronovasrl.com> <20180606094942.71190-4-giulio.benetti@micronovasrl.com> <069f5cd3309e83d13c74929f240720b232ea7251.camel@linux.intel.com> <0bc400b1-6178-2021-c9a3-3190d1a1de32@micronovasrl.com> <2abe2137e699e5ae3100b97316da469f6d1c9bb9.camel@linux.intel.com> From: Giulio Benetti Message-ID: Date: Wed, 6 Jun 2018 21:15:15 +0200 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: it Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Il 06/06/2018 20:55, Matwey V. Kornilov ha scritto: > 2018-06-06 16:11 GMT+03:00 Andy Shevchenko : >> On Wed, 2018-06-06 at 14:15 +0200, Giulio Benetti wrote: >>> Il 06/06/2018 13:56, Andy Shevchenko ha scritto: >>>> On Wed, 2018-06-06 at 11:49 +0200, Giulio Benetti wrote: >>>>> em485 gets lost during >>>>> >>>>> Copy em485 to final uart port. >>>>> >>>> >>>> Is it needed at all? >>>> >>>> The individual driver decides either to use software emulation (and >>>> calls explicitly serial8250_em485_init() for that) or do HW assisted >>>> stuff. >>> >>> In 8250_dw.c, during probe(), I need to call dw8250_rs485_config() >>> against local struct uart_8250_port uart = {}; >>> Inside serial8250_register_8250_port() not all uart fields are >>> copied(em485 too). >>> So after probe, em485 is NULL. >>> >>> Another way could be to call dw8250_rs485_config() against real uart >>> port, after calling serial8250_register_8250_port(), >>> would it make sense? >> >> Look at OMAP case closely. They have a callback to configure RS485 which >> is called in uart_set_rs485_config() which is called whenever user >> space does TIOCGRS485 IOCTL. >> >> So, it's completely driven by user space which makes sense by my >> opinion. > > AFAIU, Giulio wants to add support for rs485-enabled-at-boot-time > device tree option (see bindings/serial/rs485.txt for reference). Yes, I want to add support for "rs485-enabled-at-boot-time" property, maybe I had to write better commit log and a cover letter. Sorry. > I suppose it is only important for use-case when rs485 used as slave > (peripheral role). It's important also for master, because RTS, if RTS_AFTER_SEND is set, remains not asserted(trasnmission) until userspace opens that serial port. Sorry again for not explaining myself well. -- Giulio Benetti CTO MICRONOVA SRL Sede: Via A. Niedda 3 - 35010 Vigonza (PD) Tel. 049/8931563 - Fax 049/8931346 Cod.Fiscale - P.IVA 02663420285 Capitale Sociale € 26.000 i.v. Iscritta al Reg. Imprese di Padova N. 02663420285 Numero R.E.A. 258642