From: Daniel Thompson <daniel.thompson@linaro.org>
To: Sumit Garg <sumit.garg@linaro.org>
Cc: kgdb-bugreport@lists.sourceforge.net,
linux-serial@vger.kernel.org, gregkh@linuxfoundation.org,
jason.wessel@windriver.com, dianders@chromium.org,
jslaby@suse.com, linux@armlinux.org.uk,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/7] tty: serial: Add poll_get_irq() to the polling interface
Date: Mon, 22 Jun 2020 16:56:24 +0100 [thread overview]
Message-ID: <20200622155624.he2vs2r3e5yzf3sl@holly.lan> (raw)
In-Reply-To: <1592835984-28613-3-git-send-email-sumit.garg@linaro.org>
On Mon, Jun 22, 2020 at 07:56:19PM +0530, Sumit Garg wrote:
> From: Daniel Thompson <daniel.thompson@linaro.org>
Sumit, to some extent this mail is me yelling at myself two years ago
although, in my defence, at the time I choose not to post it because I
knew it wasn't right.
I'm a bit concerned to see the TODO: comment critiquing this interface
being removed (from patch 3) without this patch being changed to
address that comment.
> Add new API: poll_get_irq() to the polling interface in order for user
> of polling interface to retrieve allocated IRQ corresponding to
> underlying serial device.
>
> Although, serial interface still works in polling mode but interrupt
> associated with serial device can be leveraged for special purposes like
> debugger(kgdb) entry.
>
> Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
> Signed-off-by: Sumit Garg <sumit.garg@linaro.org>
> ---
> drivers/tty/serial/serial_core.c | 18 ++++++++++++++++++
> include/linux/serial_core.h | 1 +
> include/linux/tty_driver.h | 1 +
> 3 files changed, 20 insertions(+)
>
> diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
> index 66a5e2f..1bb033c 100644
> --- a/drivers/tty/serial/serial_core.c
> +++ b/drivers/tty/serial/serial_core.c
> @@ -2470,6 +2470,23 @@ static void uart_poll_put_char(struct tty_driver *driver, int line, char ch)
> port->ops->poll_put_char(port, ch);
> uart_port_deref(port);
> }
> +
> +static int uart_poll_get_irq(struct tty_driver *driver, int line)
> +{
> + struct uart_driver *drv = driver->driver_state;
> + struct uart_state *state = drv->state + line;
> + struct uart_port *port;
> + int ret = -ENODEV;
> +
> + port = uart_port_ref(state);
> + if (port && port->ops->poll_get_irq) {
> + ret = port->ops->poll_get_irq(port);
> + uart_port_deref(port);
> + }
> +
> + return ret;
> +}
> +
> #endif
>
> static const struct tty_operations uart_ops = {
> @@ -2505,6 +2522,7 @@ static const struct tty_operations uart_ops = {
> .poll_init = uart_poll_init,
> .poll_get_char = uart_poll_get_char,
> .poll_put_char = uart_poll_put_char,
> + .poll_get_irq = uart_poll_get_irq,
The TODO comments claimed this API was bogus because it doesn't permit
a free and that can cause interoperation problems with the real serial
driver. I'll cover some of that in a reply to patch 3 but for now.
Anyhow, for this patch, what are the expected semantics for
uart_poll_get_irq().
In particular how do they ensure correct interlocking with the real
serial driver underlying it (if kgdb_nmi is active on a serial port
then the underlying driver better not be active at the same time).
Daniel.
> #endif
> };
>
> diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
> index 92f5eba..8b132e6 100644
> --- a/include/linux/serial_core.h
> +++ b/include/linux/serial_core.h
> @@ -78,6 +78,7 @@ struct uart_ops {
> int (*poll_init)(struct uart_port *);
> void (*poll_put_char)(struct uart_port *, unsigned char);
> int (*poll_get_char)(struct uart_port *);
> + int (*poll_get_irq)(struct uart_port *);
> #endif
> };
>
> diff --git a/include/linux/tty_driver.h b/include/linux/tty_driver.h
> index 3584462..d6da5c5 100644
> --- a/include/linux/tty_driver.h
> +++ b/include/linux/tty_driver.h
> @@ -295,6 +295,7 @@ struct tty_operations {
> int (*poll_init)(struct tty_driver *driver, int line, char *options);
> int (*poll_get_char)(struct tty_driver *driver, int line);
> void (*poll_put_char)(struct tty_driver *driver, int line, char ch);
> + int (*poll_get_irq)(struct tty_driver *driver, int line);
> #endif
> int (*proc_show)(struct seq_file *, void *);
> } __randomize_layout;
> --
> 2.7.4
>
next prev parent reply other threads:[~2020-06-22 15:56 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-22 14:26 [PATCH 0/7] Enable support for kgdb NMI console feature Sumit Garg
2020-06-22 14:26 ` [PATCH 1/7] serial: kgdb_nmi: Allow NMI console to replace kgdb IO console Sumit Garg
2020-06-22 14:26 ` [PATCH 2/7] tty: serial: Add poll_get_irq() to the polling interface Sumit Garg
2020-06-22 15:56 ` Daniel Thompson [this message]
2020-06-23 7:48 ` Sumit Garg
2020-06-23 10:52 ` Daniel Thompson
2020-06-22 14:26 ` [PATCH 3/7] kgdb: Add request_nmi() to the io ops table for kgdboc Sumit Garg
2020-06-22 16:03 ` Daniel Thompson
2020-06-23 8:37 ` Sumit Garg
2020-06-23 10:59 ` Daniel Thompson
2020-06-26 19:44 ` Doug Anderson
2020-06-29 11:45 ` Daniel Thompson
2020-06-30 6:09 ` Sumit Garg
2020-06-22 14:26 ` [PATCH 4/7] serial: kgdb_nmi: Add support for interrupt based fallback Sumit Garg
2020-06-22 16:36 ` Daniel Thompson
2020-06-23 9:59 ` Sumit Garg
2020-06-22 14:26 ` [PATCH 5/7] serial: 8250: Implement poll_get_irq() interface Sumit Garg
2020-06-22 14:26 ` [PATCH 6/7] serial: amba-pl011: " Sumit Garg
2020-06-22 14:26 ` [PATCH 7/7] serial: kgdb_nmi: Replace hrtimer with irq_work ping Sumit Garg
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20200622155624.he2vs2r3e5yzf3sl@holly.lan \
--to=daniel.thompson@linaro.org \
--cc=dianders@chromium.org \
--cc=gregkh@linuxfoundation.org \
--cc=jason.wessel@windriver.com \
--cc=jslaby@suse.com \
--cc=kgdb-bugreport@lists.sourceforge.net \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-serial@vger.kernel.org \
--cc=linux@armlinux.org.uk \
--cc=sumit.garg@linaro.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).