Re: [patch 02/13] powerpc: add hvc backend for rtas

Olof Johansson
2006-03-23T21:32:59Z

Hi,

I have a couple of nitpicks below, nothing major.

Since it's such a simple driver, it's easy to use as a base for similar
ones, and as such it'd be nice to have it as clean as possible to avoid
others to inherit strangeness.

-Olof

On Thu, Mar 23, 2006 at 12:00:02AM +0100, Arnd Bergmann wrote:

> +static inline int hvc_rtas_write_console(uint32_t vtermno, const char *buf, int count)
> +{
> + int done;
> +
> + /* if there is more than one character to be displayed, wait a bit */
> + for (done = 0; done < count; done++) {
> + int result;
> + result = rtas_call(rtascons_put_char_token, 1, 1, NULL, buf[done]);
> + if (result)
> + break;

Why introduce a scope-local variable just to check it?
if(rtas_call(...)) would be cleaner.

> + }
> + /* the calling routine expects to receive the number of bytes sent */
> + return done;
> +}
> +
> +static int hvc_rtas_read_console(uint32_t vtermno, char *buf, int count)
> +{
> + int i;
> +
> + for (i = 0; i < count; i++) {
> + int c, err;
> +
> + err = rtas_call(rtascons_get_char_token, 0, 2, &c);
> + if (err)
> + break;

Same here

> +
> + buf[i] = c;
> + }
> +
> + return i;
> +}
> +
> +static struct hv_ops hvc_rtas_get_put_ops = {
> + .get_chars = hvc_rtas_read_console,
> + .put_chars = hvc_rtas_write_console,
> +};
> +
> +static int hvc_rtas_init(void)
> +{
> + struct hvc_struct *hp;
> +
> + if (rtascons_put_char_token == RTAS_UNKNOWN_SERVICE)
> + rtascons_put_char_token = rtas_token("put-term-char");
> + if (rtascons_put_char_token == RTAS_UNKNOWN_SERVICE)
> + return -EIO;
> +
> + if (rtascons_get_char_token == RTAS_UNKNOWN_SERVICE)
> + rtascons_get_char_token = rtas_token("get-term-char");
> + if (rtascons_get_char_token == RTAS_UNKNOWN_SERVICE)
> + return -EIO;
> +
> + BUG_ON(hvc_rtas_dev);
> +
> + /* Allocate an hvc_struct for the console device we instantiated
> + * earlier. Save off hp so that we can return it on exit */
> + hp = hvc_alloc(hvc_rtas_cookie, NO_IRQ, &hvc_rtas_get_put_ops);
> + if (IS_ERR(hp))
> + return PTR_ERR(hp);
> + hvc_rtas_dev = hp;
> + return 0;
> +}
> +module_init(hvc_rtas_init);
> +
> +/* This will tear down the tty portion of the driver */
> +static void __exit hvc_rtas_exit(void)
> +{
> + /* Really the fun isn't over until the worker thread breaks down and the
> + * tty cleans up */
> + if (hvc_rtas_dev)
> + hvc_remove(hvc_rtas_dev);
> +}
> +module_exit(hvc_rtas_exit); /* before drivers/char/hvc_console.c */

Cryptic comment?

> +/* This will happen prior to module init. There is no tty at this time? */
> +static int hvc_rtas_console_init(void)
> +{
> + rtascons_put_char_token = rtas_token("put-term-char");
> + if (rtascons_put_char_token == RTAS_UNKNOWN_SERVICE)
> + return -EIO;
> + rtascons_get_char_token = rtas_token("get-term-char");
> + if (rtascons_get_char_token == RTAS_UNKNOWN_SERVICE)
> + return -EIO;
> +
> + hvc_instantiate(hvc_rtas_cookie, 0, &hvc_rtas_get_put_ops );
> + add_preferred_console("hvc", 0, NULL);
> + return 0;
> +}
> +console_initcall(hvc_rtas_console_init);
> Index: linus-2.6/drivers/char/Makefile
> ===================================================================
> --- linus-2.6.orig/drivers/char/Makefile
> +++ linus-2.6/drivers/char/Makefile
> @@ -43,6 +43,7 @@ obj-$(CONFIG_SX) += sx.o generic_serial
> obj-$(CONFIG_RIO) += rio/ generic_serial.o
> obj-$(CONFIG_HVC_DRIVER) += hvc_console.o
> obj-$(CONFIG_HVC_CONSOLE) += hvc_vio.o hvsi.o
> +obj-$(CONFIG_HVC_RTAS) += hvc_rtas.o
> obj-$(CONFIG_RAW_DRIVER) += raw.o
> obj-$(CONFIG_SGI_SNSC) += snsc.o snsc_event.o
> obj-$(CONFIG_MMTIMER) += mmtimer.o
> Index: linus-2.6/drivers/char/Kconfig
> ===================================================================
> --- linus-2.6.orig/drivers/char/Kconfig
> +++ linus-2.6/drivers/char/Kconfig
> @@ -578,6 +578,13 @@ config HVC_CONSOLE
> console. This driver allows each pSeries partition to have a console
> which is accessed via the HMC.
>
> +config HVC_RTAS
> + bool "IBM RTAS Console support"
> + depends on PPC_RTAS
> + select HVC_DRIVER
> + help
> + IBM Console device driver which makes use of RTAS
> +
> config HVCS
> tristate "IBM Hypervisor Virtual Console Server support"
> depends on PPC_PSERIES
>
> --
>
> -
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