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Tue, 3 Jul 2018 02:25:12 +0000 Date: Tue, 3 Jul 2018 10:22:57 +0800 From: Jisheng Zhang To: Andy Shevchenko Cc: Greg Kroah-Hartman , Jiri Slaby , , , Subject: Re: [PATCH 0/2] serial: 8250_dw: add fractional divisor support Message-ID: <20180703102257.678db6a8@xhacker.debian> In-Reply-To: <59b14f97234271a7d859fa07f27bd66ec252ccc9.camel@linux.intel.com> References: <20180702180428.331b36c5@xhacker.debian> <59b14f97234271a7d859fa07f27bd66ec252ccc9.camel@linux.intel.com> X-Mailer: Claws Mail 3.16.0 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Originating-IP: [124.74.246.114] X-ClientProxiedBy: TY2PR01CA0001.jpnprd01.prod.outlook.com (2603:1096:404:a::13) To MWHPR03MB2640.namprd03.prod.outlook.com (2603:10b6:300:46::10) X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 9ba2a934-37ba-47a0-6a49-08d5e08c35e3 X-Microsoft-Antispam: UriScan:;BCL:0;PCL:0;RULEID:(7020095)(4652040)(8989117)(5600053)(711020)(4534165)(4627221)(201703031133081)(201702281549075)(8990107)(2017052603328)(7153060)(7193020);SRVR:MWHPR03MB2640; 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The fractional divisor width > > > is > > > 4bits ~ 6bits. > > > > > > > There are several serial IPs that have fractional divider built-in. > > None > > is using any specific hooks. Why do you need in your case, esp. taking > > into consideration that we have a custom ->set_termios() callback? > > Okay, I see that in 8250 we have hooks embedded into 8250_port.c which > is not the best solution. > > For example it prevents better splitting Exar code. > So, we would need these hooks, but better to integrate them in the same > way like it's done for the rest of 8250 ones, i.e. > - rename existing to have a "do" word > - create new functions which would be a replacement that choose between > "do" variant and custom one > - not sure if we need to export "do" variants (at least for now) So you mean add the support as following: 1.rename current serial8250_set_divisor as serial8250_do_set_divisor 2.add a new serial8250_set_divisor which will be as simple as static void serial8250_set_divisor(struct uart_port *port, ...) { struct uart_8250_port *up = up_to_u8250p(port); if (up->set_divisor) up->set_divisor(...); else serial8250_do_set_divisor(...); } could you please confirm? Another issue is I'm not sure which struct to add the hook, struct uart_port or struct uart_8250_port? Currently, it seems that only uart_8250_port needs this hook, sure, adding the hook to struct uart_port is fine either. Could you please kindly give some suggestions? Thanks, Jisheng