On Wed, 7 Sep 2022, Greg Kroah-Hartman wrote: > On Wed, Sep 07, 2022 at 03:21:28PM +0300, Ilpo Järvinen wrote: > > On Wed, 7 Sep 2022, Arnd Bergmann wrote: > > > > > On Wed, Sep 7, 2022, at 12:16 PM, Ilpo Järvinen wrote: > > > > On Wed, 7 Sep 2022, Jiri Slaby wrote: > > > >> On 06. 09. 22, 13:30, Johan Hovold wrote: > > > >> > On Tue, Sep 06, 2022 at 12:48:01PM +0200, Jiri Slaby wrote: > > > >> > NAK > > > >> > > > >> I'd love to come up with something nicer. That would be a function in > > > >> serial-core calling hooks like I had [1] for example. But provided all those > > > >> CPU workarounds/thunks, it'd be quite expensive to call two functions per > > > >> character. > > > >> > > > >> Or creating a static inline (having ± the macro content) and the hooks as > > > >> parameters and hope for optimizations to eliminate thunks (also suggested in > > > >> the past [1]). > > > >> > > > >> [1] https://lore.kernel.org/all/20220411105405.9519-1-jslaby@xxxxxxx/ > > > > > > > > I second Jiri here. > > > > > > > > Saving lines in drivers is not that important compared with all removing > > > > all the variants of the same thing that have crept there over the years. > > > > > > > > I suspect the main reason for the variants is that everybody just used > > > > other drivers as examples and therefore we've a few "main" variant > > > > branches depending on which of the drivers was used as an example for the > > > > other. That is hardly a good enough reason to keep them different and as > > > > long as each driver keeps its own function for this, it will eventually > > > > lead to similar differentiation so e.g. a one-time band-aid similarization > > > > would not help in the long run. > > > > > > > > Also, I don't understand why you see it unreadable when the actual code is > > > > out in the open in that macro. It's formatted much better than e.g. > > > > read_poll_timeout() if you want an example of something that is hardly > > > > readable ;-). I agree though there's a learning-curve, albeit small, that > > > > it actually creates a function but that doesn't seem to me as big of an > > > > obstacle you seem to think. > > > > > > I think it would help to replace the macro that defines > > > the function with a set of macros that can be used in > > > function bodies. This would avoid the __VA_ARGS__ stuff > > > and allow readers that are unfamiliar with tty drivers to > > > treat it as a function call. > > > > > > So e.g. instead of > > > > > > static DEFINE_UART_PORT_TX_HELPER_LIMITED(altera_jtaguart_do_tx_chars, > > > true, > > > writel(ch, port->membase + ALTERA_JTAGUART_DATA_REG), > > > ({})); > > > > > > the altera_jtaguart driver would contain a function like > > > > > > static int altera_jtaguart_do_tx_chars(struct uart_port *port, > > > unsigned int count) > > > { > > > char ch; > > > > > > return uart_port_tx_helper_limited(port, ch, count, true, > > > writel(ch, port->membase + ALTERA_JTAGUART_DATA_REG), > > > ({})); > > > } > > > > > > or some variation of that. It's a few more lines, but those > > > extra lines would help me understand what is actually going on > > > while still avoiding the usual bugs and duplication. > > > > > > If the caller of that function is itself trivial (like > > > serial21285_tx_chars), then the intermediate function can > > > be omitted in order to save some of the extra complexity. > > > > I'd be ok with that. There's still a small startle factor associated to > > passing that writel(...) as an argument to a "function" but it's the same > > for other things such as read_poll_timeout() so not an end of the world. > > That's going to incure the function-pointer-indirection-call for every > character that Jiri's original submission had, so I don't think this is > a very viable solution, sorry. I don't think you got what Arnd meant. It must still be technically a #define because you cannot pass writel(ch, port->membase + ALTERA_JTAGUART_DATA_REG) as an argument to a real function like he did in the example above. It's similar to how read_poll_timeout() and friends are #defines despite being lowercased. -- i.
