[PATCH v1 1/1] hvc_console: Allow backends to set I/O buffer size

[Christophe Leroy]

Hi,

Le 15/01/2023 à 20:56, Geoff Levand a écrit :
> To allow HVC backends to set the I/O buffer sizes to values that are most
> efficient for the backend, change the macro definitions where the buffer sizes
> are set to be conditional on whether or not the macros are already defined.
> Also, rename the macros from N_OUTBUF to HVC_N_OUBUF and from N_INBUF to
> HVC_N_INBUF.
> 
> Typical usage in the backend source file would be:
> 
>    #define HVC_N_OUTBUF 32
>    #define HVC_N_INBUF 32
>    #include "hvc_console.h"
> 
> Signed-off-by: Geoff Levand <geoff at infradead.org>

Most patches in drivers/tty/hvc/ are merged by greg through the serial 
tree, you should send to him.

And I think it is not correct to send that as pull request.

Christophe

> ---
> 
> Hi,
> 
> With this patch the buffer sizes are set by defining preprocessor macros before
> including the hvc_console.h header file.  Another way would be to have Kconfig
> options for the buffer sizes.  Since the optimal buffer size is so closely tied
> to the backend implementation I thought that using these preprocessor macros
> would be the better way.
> 
> -Geoff
> 
> The following changes since commit 5dc4c995db9eb45f6373a956eb1f69460e69e6d4:
> 
>    Linux 6.2-rc4 (2023-01-15 09:22:43 -0600)
> 
> are available in the Git repository at:
> 
>    git://git.kernel.org/pub/scm/linux/kernel/git/geoff/ps3-linux.git for-merge-hvc-v1
> 
> for you to fetch changes up to 8f3cd1e0589f134380f80a1f551c8232ed0bc1f2:
> 
>    hvc_console: Allow backends to set I/O buffer size (2023-01-15 09:36:22 -0800)
> 
> 
>   drivers/tty/hvc/hvc_console.c | 19 +++++++++++--------
>   1 file changed, 11 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/tty/hvc/hvc_console.c b/drivers/tty/hvc/hvc_console.c
> index a683e21df19c..f7809d19e2cd 100644
> --- a/drivers/tty/hvc/hvc_console.c
> +++ b/drivers/tty/hvc/hvc_console.c
> @@ -42,12 +42,15 @@
>   #define HVC_CLOSE_WAIT (HZ/100) /* 1/10 of a second */
>   
>   /*
> - * These sizes are most efficient for vio, because they are the
> - * native transfer size. We could make them selectable in the
> - * future to better deal with backends that want other buffer sizes.
> + * These default sizes are most efficient for vio, because they are
> + * the native transfer size.
>    */
> -#define N_OUTBUF	16
> -#define N_INBUF		16
> +#if !defined(HVC_N_OUTBUF)
> +# define HVC_N_OUTBUF	16
> +#endif
> +#if !defined(HVC_N_INBUF)
> +# define HVC_N_INBUF	16
> +#endif
>   
>   #define __ALIGNED__ __attribute__((__aligned__(L1_CACHE_BYTES)))
>   
> @@ -151,7 +154,7 @@ static uint32_t vtermnos[MAX_NR_HVC_CONSOLES] =
>   static void hvc_console_print(struct console *co, const char *b,
>   			      unsigned count)
>   {
> -	char c[N_OUTBUF] __ALIGNED__;
> +	char c[HVC_N_OUTBUF] __ALIGNED__;
>   	unsigned i = 0, n = 0;
>   	int r, donecr = 0, index = co->index;
>   
> @@ -633,7 +636,7 @@ static int __hvc_poll(struct hvc_struct *hp, bool may_sleep)
>   {
>   	struct tty_struct *tty;
>   	int i, n, count, poll_mask = 0;
> -	char buf[N_INBUF] __ALIGNED__;
> +	char buf[HVC_N_INBUF] __ALIGNED__;
>   	unsigned long flags;
>   	int read_total = 0;
>   	int written_total = 0;
> @@ -674,7 +677,7 @@ static int __hvc_poll(struct hvc_struct *hp, bool may_sleep)
>   
>    read_again:
>   	/* Read data if any */
> -	count = tty_buffer_request_room(&hp->port, N_INBUF);
> +	count = tty_buffer_request_room(&hp->port, HVC_N_INBUF);
>   
>   	/* If flip is full, just reschedule a later read */
>   	if (count == 0) {