From: Joe Perches joe@perches.com Sent: Tuesday, April 20, 2021 12:59 PM

On Tue, 2021-04-20 at 08:44 -0700, Michael Kelley wrote:

...

Due to a full ring buffer, the driver may be unable to send updates to the Hyper-V host. But outputing the error message can make the problem worse because console output is also typically written to the frame buffer. As a result, in some circumstances the error message is output continuously.

Break the cycle by rate limiting the error message. Also output the error code for additional diagnosability.

Signed-off-by: Michael Kelley mikelley@microsoft.com

None of the callers of this function ever check the return status. Why is important/useful to emit this message at all?

Except during device initialization, the messages tell Hyper-V about updates to the frame buffer contents. The fbdev framework functions (such as fillrect) that eventually call synthvid_send() are void functions. So the message is the only alert that something has gone wrong in the communication with Hyper-V, which makes it useful for diagnostic purposes.

Michael

...

---

drivers/video/fbdev/hyperv_fb.c | 2 +-  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/video/fbdev/hyperv_fb.c b/drivers/video/fbdev/hyperv_fb.c index 4dc9077..a7e6eea 100644 --- a/drivers/video/fbdev/hyperv_fb.c +++ b/drivers/video/fbdev/hyperv_fb.c @@ -308,7 +308,7 @@ static inline int synthvid_send(struct hv_device *hdev,   VM_PKT_DATA_INBAND, 0);

if (ret)

• pr_err("Unable to send packet via vmbus\n");
  

• pr_err_ratelimited("Unable to send packet via vmbus; error %d\n", ret);
  
  
  

return ret;  }