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. -- i.
