linux-kernel - Re: [PATCH V2] staging: gpib: Change return type and error code of fluke_get_dma

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Message-ID: <10af294f-97db-4af6-949d-8be778277157@linuxfoundation.org>
Date: Thu, 17 Oct 2024 11:13:39 -0600
From: Shuah Khan <skhan@...uxfoundation.org>
To: "Everest K.C." <everestkc@...restkc.com.np>, dpenkler@...il.com,
 gregkh@...uxfoundation.org
Cc: dan.carpenter@...aro.org, linux-staging@...ts.linux.dev,
 linux-kernel@...r.kernel.org, Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [PATCH V2] staging: gpib: Change return type and error code of
 fluke_get_dma_residue

On 10/17/24 03:25, Everest K.C. wrote:
> fluke_get_dma_residue() returns unsigned int with -1 as error code.
> This error cannot be caught.
> Fix this by changing the return type of the function to int and
> returning the error code, that was captured. Also, change the data
> type of variable residue to int in the function fluke_dma_read().> 
> Fixes: 55936779f496 ("staging: gpib: Add Fluke cda based cards GPIB driver")
> Signed-off-by: Everest K.C. <everestkc@...restkc.com.np>
> ---
> V1 -> V2: - Fixed the caller
> 	  - Updated the changelog
> 
>   drivers/staging/gpib/eastwood/fluke_gpib.c | 6 +++---
>   1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/staging/gpib/eastwood/fluke_gpib.c b/drivers/staging/gpib/eastwood/fluke_gpib.c
> index f9f149db222d..378687eb619f 100644
> --- a/drivers/staging/gpib/eastwood/fluke_gpib.c
> +++ b/drivers/staging/gpib/eastwood/fluke_gpib.c
> @@ -536,7 +536,7 @@ static int fluke_accel_write(gpib_board_t *board, uint8_t *buffer, size_t length
>   	return 0;
>   }
>   
> -static unsigned int fluke_get_dma_residue(struct dma_chan *chan, dma_cookie_t cookie)
> +static int fluke_get_dma_residue(struct dma_chan *chan, dma_cookie_t cookie)
>   {
>   	struct dma_tx_state state;
>   	int result;
> @@ -544,7 +544,7 @@ static unsigned int fluke_get_dma_residue(struct dma_chan *chan, dma_cookie_t co
>   	result = dmaengine_pause(chan);

As a side note, out of 21  dmaengine_pause() callers, just 3 check
the return value, spanning spi, stanging, tty, sound: core and soc

This exact same problem is in staging/gpib/fmh_gpib/fmh_gpib.c
unsigned int fmh_gpib_get_dma_residue() returns -1

>   	if (result < 0) {
>   		pr_err("fluke_gpib: dma pause failed?\n");

This could be a dev_err using dma_chan_dev

> -		return -1;
> +		return result;
>   	}
>   	dmaengine_tx_status(chan, cookie, &state);
>   	// hardware doesn't support resume, so dont call this
> @@ -559,7 +559,7 @@ static int fluke_dma_read(gpib_board_t *board, uint8_t *buffer,
>   	struct nec7210_priv *nec_priv = &e_priv->nec7210_priv;
>   	int retval = 0;
>   	unsigned long flags;
> -	unsigned int residue;
> +	int residue;
>   	dma_addr_t bus_address;
>   	struct dma_async_tx_descriptor *tx_desc;
>   	dma_cookie_t dma_cookie;

Looks good to me.

Reviewed-by: Shuah Khan <skhan@...uxfoundation.org>

thanks,
-- Shuah