linux-kernel - Re: [PATCH] mhi_bus: core: Return EBUSY if MHI ring is full

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Date:   Tue, 16 Feb 2021 12:22:51 -0800
From:   Bhaumik Bhatt <bbhatt@...eaurora.org>
To:     Jeffrey Hugo <jhugo@...eaurora.org>
Cc:     manivannan.sadhasivam@...aro.org, hemantk@...eaurora.org,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Fan Wu <wufan@...eaurora.org>,
        jhugo=codeaurora.org@...eaurora.org
Subject: Re: [PATCH] mhi_bus: core: Return EBUSY if MHI ring is full

On 2021-02-16 10:48 AM, Jeffrey Hugo wrote:
> From: Fan Wu <wufan@...eaurora.org>
> 
> Currently ENOMEM is returned when MHI ring is full. This error code is
> very misleading. Change to EBUSY instead.
> 
> Signed-off-by: Fan Wu <wufan@...eaurora.org>
> Signed-off-by: Jeffrey Hugo <jhugo@...eaurora.org>
> ---
>  drivers/bus/mhi/core/main.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/bus/mhi/core/main.c b/drivers/bus/mhi/core/main.c
> index f182736..21eb5fc 100644
> --- a/drivers/bus/mhi/core/main.c
> +++ b/drivers/bus/mhi/core/main.c
> @@ -996,7 +996,7 @@ static int mhi_queue(struct mhi_device *mhi_dev,
> struct mhi_buf_info *buf_info,
> 
>  	ret = mhi_is_ring_full(mhi_cntrl, tre_ring);
>  	if (unlikely(ret)) {
> -		ret = -ENOMEM;
> +		ret = -EBUSY;
>  		goto exit_unlock;
>  	}

ENOMEM is descriptive of the state of the ring since you basically 
cannot queue any
more packets as no memory is currently available.

But I agree, it can be misleading for this API. How about EAGAIN in 
place of EBUSY,
which tells the user to try the queue attempt again implying memory 
should become
available as more elements are consumed by the device/client?

Thanks,
Bhaumik
---
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