Pranavkumar Sawargaonkar pranavkumar@linaro.org writes:
Hi Rusty,
On 13 May 2013 08:22, Rusty Russell rusty@rustcorp.com.au wrote:
Pranavkumar Sawargaonkar pranavkumar@linaro.org writes:
Signed-off-by: Pranavkumar Sawargaonkar pranavkumar@linaro.org Signed-off-by: Anup Patel anup.patel@linaro.org
Documentation/virtual/virtio-spec.txt | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-)
OK, I applied this to the lyx master, with three changes:
Changed "filed" to "field".
Added ", or even acknowledging the feature" after "without initializing virtio queues".
Added an initial point to the Device Initialization section:
- If the VIRTIO_CONSOLE_F_EMERG_WRITE feature is offered, the
emerg_wr field of the configuration can be written at any time. Thus it should work for very early boot debugging output as well as catastophic OS failures (eg. virtio ring corruption).
Thanks for applying this patch. Have you also applied first patch ([PATCH V2 1/3] virtio: console: Add emergency writeonly register to config space) with this? (https://lkml.org/lkml/2013/5/6/169)
Would like Amit's Ack, since he's de-facto console maintainer.
I've reproduced it below.
Cheers, Rusty.
Subject: [PATCH V2 1/3] virtio: console: Add emergency writeonly register to config space Date: Mon, 6 May 2013 17:49:49 +0530 Message-Id: 1367842791-30285-2-git-send-email-pranavkumar@linaro.org X-Mailer: git-send-email 1.7.9.5 In-Reply-To: 1367842791-30285-1-git-send-email-pranavkumar@linaro.org References: 1367842791-30285-1-git-send-email-pranavkumar@linaro.org X-Gm-Message-State: ALoCoQmDOoCdPmDpT+VgLwYAlJHmkUTB8sEAHVSbrNxWBzYgPHFT9rQ2A9dR8fToM81cHDZDppGx
This patch adds an emerg_wr register (writeonly) in config space of virtio console device which can be used for debugging.
Signed-off-by: Pranavkumar Sawargaonkar pranavkumar@linaro.org Signed-off-by: Anup Patel anup.patel@linaro.org Signed-off-by: Rusty Russell rusty@rustcorp.com.au --- include/uapi/linux/virtio_console.h | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/include/uapi/linux/virtio_console.h b/include/uapi/linux/virtio_console.h index ee13ab6..3fd0dce 100644 --- a/include/uapi/linux/virtio_console.h +++ b/include/uapi/linux/virtio_console.h @@ -38,6 +38,7 @@ /* Feature bits */ #define VIRTIO_CONSOLE_F_SIZE 0 /* Does host provide console size? */ #define VIRTIO_CONSOLE_F_MULTIPORT 1 /* Does host provide multiple ports? */ +#define VIRTIO_CONSOLE_F_EMERG_WRITE 2 /* Does host support emergency write? */
#define VIRTIO_CONSOLE_BAD_ID (~(u32)0)
@@ -48,6 +49,8 @@ struct virtio_console_config { __u16 rows; /* max. number of ports this device can hold */ __u32 max_nr_ports; + /* emergency write register */ + __u32 emerg_wr; } __attribute__((packed));
/*