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Date: Thu, 6 Oct 2022 15:24:16 -0700 (PDT) From: matthew.gerlach@...ux.intel.com To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com> cc: hao.wu@...el.com, yilun.xu@...el.com, russell.h.weight@...el.com, basheer.ahmed.muddebihal@...el.com, trix@...hat.com, mdf@...nel.org, linux-fpga@...r.kernel.org, linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org, tianfei.zhang@...el.com, corbet@....net, gregkh@...uxfoundation.org, linux-serial@...r.kernel.org, jirislaby@...nel.org, geert+renesas@...der.be, niklas.soderlund+renesas@...natech.se, macro@...am.me.uk, johan@...nel.org, lukas@...ner.de, kernel test robot <lkp@...el.com> Subject: Re: [PATCH v3 4/4] tty: serial: 8250: add DFL bus driver for Altera 16550. On Thu, 6 Oct 2022, Andy Shevchenko wrote: > On Thu, Oct 06, 2022 at 10:00:43AM -0700, matthew.gerlach@...ux.intel.com wrote: >> On Tue, 4 Oct 2022, Andy Shevchenko wrote: >>> On Tue, Oct 04, 2022 at 07:37:18AM -0700, matthew.gerlach@...ux.intel.com wrote: > > ... > >>>> Reported-by: kernel test robot <lkp@...el.com> >>> >>> https://docs.kernel.org/process/submitting-patches.html?highlight=reported#using-reported-by-tested-by-reviewed-by-suggested-by-and-fixes >>> >>> "The Reported-by tag gives credit to people who find bugs and report them and it >>> hopefully inspires them to help us again in the future. Please note that if the >>> bug was reported in private, then ask for permission first before using the >>> Reported-by tag. The tag is intended for bugs; please do not use it to credit >>> feature requests." >> >> The kernel test robot did find a bug in my v1 submission. I was missing the >> static keyword for a function declaration. Should I remove the tag? > > What's yours take from the above documentation? > Since the kernel test robot did find a bug. The tag should stay. > ... > >>>> + dfh_base = devm_ioremap_resource(dev, &dfl_dev->mmio_res); >>>> + if (IS_ERR(dfh_base)) >>>> + return PTR_ERR(dfh_base); >>>> + >>>> + res_size = resource_size(&dfl_dev->mmio_res); >>>> + >>>> + ret = dfl_uart_get_params(dev, dfh_base, res_size, &uart); >>> >>>> + devm_iounmap(dev, dfh_base); >>>> + devm_release_mem_region(dev, dfl_dev->mmio_res.start, res_size); >>> >>> If it's temporary, may be you shouldn't even consider devm_ioremap_resource() >>> to begin with? The devm_* release type of functions in 99% of the cases >>> indicate of the abusing devm_. >> >> I will change the code to call ioremap() and request_mem_region() directly >> instead of the devm_ versions. > > But why will you need request_mem_region() in that case? It doesn't seem that I need to call request_mem_regsion; so I will skip it. > >>>> + if (ret < 0) >>>> + return dev_err_probe(dev, ret, "failed uart feature walk\n"); > > ... > >>>> +config SERIAL_8250_DFL >>>> + tristate "DFL bus driver for Altera 16550 UART" >>>> + depends on SERIAL_8250 && FPGA_DFL >>>> + help >>>> + This option enables support for a Device Feature List (DFL) bus >>>> + driver for the Altera 16650 UART. One or more Altera 16650 UARTs >>>> + can be instantiated in a FPGA and then be discovered during >>>> + enumeration of the DFL bus. >>> >>> When m, what be the module name? >> >> I see the file, kernel/drivers/tty/serial/8250/8250_dfl.ko, installed into >> /lib/modules/... I also see "alias dfl:t0000f0024* 8250_dfl" in >> modules.alias > > My point is that user who will run `make menuconfig` will read this and have > no clue after the kernel build if the module was built or not. Look into other > (recent) sections of the Kconfig for drivers in the kernel for how they inform > user about the module name (this more or less standard pattern you just need > to copy'n'paste'n'edit carefully). > > ... I think this should be added: To compile this driver as a module, chose M here: the module will be called 8250_dfl. > >>>> obj-$(CONFIG_SERIAL_8250_FOURPORT) += 8250_fourport.o >>>> obj-$(CONFIG_SERIAL_8250_ACCENT) += 8250_accent.o >>>> obj-$(CONFIG_SERIAL_8250_BOCA) += 8250_boca.o >>>> +obj-$(CONFIG_SERIAL_8250_DFL) += 8250_dfl.o >>> >>> This group of drivers for the 4 UARTs on the board or so, does FPGA belong to >>> it? (Same Q, btw, for the Kconfig section. And yes, I know that some of the >>> entries are not properly placed there and in Makefile.) >> >> Since 8250_dfl results in its own module, and my kernel config doesn't have >> FOURPORT, ACCENT, nor BOCA, I guess I don't understand the problem. > > The Makefile is a bit chaotic, but try to find the sorted (more or less) > group of drivers that are not 4 ports and squeeze your entry there > (I expect somewhere between the LPSS/MID lines). > > It will help to sort out that mess in the future. I will move 8250_dfl between LPSS and MID lines in the Makefile. Should I move the definition in Kconfig to be between LPSS and MID to be consistent? > >>>> obj-$(CONFIG_SERIAL_8250_EXAR_ST16C554) += 8250_exar_st16c554.o >>>> obj-$(CONFIG_SERIAL_8250_HUB6) += 8250_hub6.o >>>> obj-$(CONFIG_SERIAL_8250_FSL) += 8250_fsl.o > > -- > With Best Regards, > Andy Shevchenko > > >
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