[PATCH next] mtd: rawnand: loongson1: Fix error code in ls1x_nand_dma_transfer()

[PATCH next] mtd: rawnand: loongson1: Fix error code in ls1x_nand_dma_transfer()

[Dan Carpenter]

The "desc" variable is NULL and PTR_ERR(NULL) is zero/success.  Return
a negative error code instead.

Fixes: d2d10ede04b1 ("mtd: rawnand: Add Loongson-1 NAND Controller Driver")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
---
It's hard to know what the patch prefix should be here.  Ideally when we
add a new driver we would use the patch prefix for the driver.

Tired: subsystem: Add driver XXX
Wired: subsystem: XXX: Add driver for XXX

 drivers/mtd/nand/raw/loongson1-nand-controller.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/mtd/nand/raw/loongson1-nand-controller.c b/drivers/mtd/nand/raw/loongson1-nand-controller.c
index 6a369b1c7d86..8754bb4f8b56 100644
--- a/drivers/mtd/nand/raw/loongson1-nand-controller.c
+++ b/drivers/mtd/nand/raw/loongson1-nand-controller.c
@@ -371,7 +371,7 @@ static int ls1x_nand_dma_transfer(struct ls1x_nand_host *host, struct ls1x_nand_
 	desc = dmaengine_prep_slave_single(chan, dma_addr, op->len, xfer_dir, DMA_PREP_INTERRUPT);
 	if (!desc) {
 		dev_err(dev, "failed to prepare DMA descriptor\n");
-		ret = PTR_ERR(desc);
+		ret = -ENOMEM;
 		goto err;
 	}
 	desc->callback = ls1x_nand_dma_callback;
-- 
2.47.2

Re: [PATCH next] mtd: rawnand: loongson1: Fix error code in ls1x_nand_dma_transfer()

[Keguang Zhang]

On Fri, May 2, 2025 at 4:39 PM Dan Carpenter <dan.carpenter@linaro.org> wrote:
>
> The "desc" variable is NULL and PTR_ERR(NULL) is zero/success.  Return
> a negative error code instead.
>
> Fixes: d2d10ede04b1 ("mtd: rawnand: Add Loongson-1 NAND Controller Driver")
> Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
> ---
> It's hard to know what the patch prefix should be here.  Ideally when we
> add a new driver we would use the patch prefix for the driver.
>
> Tired: subsystem: Add driver XXX
> Wired: subsystem: XXX: Add driver for XXX
>
>  drivers/mtd/nand/raw/loongson1-nand-controller.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/mtd/nand/raw/loongson1-nand-controller.c b/drivers/mtd/nand/raw/loongson1-nand-controller.c
> index 6a369b1c7d86..8754bb4f8b56 100644
> --- a/drivers/mtd/nand/raw/loongson1-nand-controller.c
> +++ b/drivers/mtd/nand/raw/loongson1-nand-controller.c
> @@ -371,7 +371,7 @@ static int ls1x_nand_dma_transfer(struct ls1x_nand_host *host, struct ls1x_nand_
>         desc = dmaengine_prep_slave_single(chan, dma_addr, op->len, xfer_dir, DMA_PREP_INTERRUPT);
>         if (!desc) {
>                 dev_err(dev, "failed to prepare DMA descriptor\n");
> -               ret = PTR_ERR(desc);
> +               ret = -ENOMEM;

Thank you for fixing this issue.
However, I believe -EIO is more appropriate than -ENOMEM, since
dmaengine_prep_slave_single() can return errors other than -ENOMEM.

>                 goto err;
>         }
>         desc->callback = ls1x_nand_dma_callback;
> --
> 2.47.2
>


-- 
Best regards,

Keguang Zhang

Re: [PATCH next] mtd: rawnand: loongson1: Fix error code in ls1x_nand_dma_transfer()

[Dan Carpenter]

On Tue, May 06, 2025 at 05:16:03PM +0800, Keguang Zhang wrote:
> On Fri, May 2, 2025 at 4:39 PM Dan Carpenter <dan.carpenter@linaro.org> wrote:
> >
> > The "desc" variable is NULL and PTR_ERR(NULL) is zero/success.  Return
> > a negative error code instead.
> >
> > Fixes: d2d10ede04b1 ("mtd: rawnand: Add Loongson-1 NAND Controller Driver")
> > Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
> > ---
> > It's hard to know what the patch prefix should be here.  Ideally when we
> > add a new driver we would use the patch prefix for the driver.
> >
> > Tired: subsystem: Add driver XXX
> > Wired: subsystem: XXX: Add driver for XXX
> >
> >  drivers/mtd/nand/raw/loongson1-nand-controller.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/mtd/nand/raw/loongson1-nand-controller.c b/drivers/mtd/nand/raw/loongson1-nand-controller.c
> > index 6a369b1c7d86..8754bb4f8b56 100644
> > --- a/drivers/mtd/nand/raw/loongson1-nand-controller.c
> > +++ b/drivers/mtd/nand/raw/loongson1-nand-controller.c
> > @@ -371,7 +371,7 @@ static int ls1x_nand_dma_transfer(struct ls1x_nand_host *host, struct ls1x_nand_
> >         desc = dmaengine_prep_slave_single(chan, dma_addr, op->len, xfer_dir, DMA_PREP_INTERRUPT);
> >         if (!desc) {
> >                 dev_err(dev, "failed to prepare DMA descriptor\n");
> > -               ret = PTR_ERR(desc);
> > +               ret = -ENOMEM;
> 
> Thank you for fixing this issue.
> However, I believe -EIO is more appropriate than -ENOMEM, since
> dmaengine_prep_slave_single() can return errors other than -ENOMEM.
> 

It's not an I/O error so -EIO isn't correct.

There are a bunch of reasons it could fail but most likely
dma_pool_alloc() failed.  I think -ENOMEM is correct.

regards,
dan carpenter

Re: [PATCH next] mtd: rawnand: loongson1: Fix error code in ls1x_nand_dma_transfer()

[Keguang Zhang]

On Tue, May 6, 2025 at 5:32 PM Dan Carpenter <dan.carpenter@linaro.org> wrote:
>
> On Tue, May 06, 2025 at 05:16:03PM +0800, Keguang Zhang wrote:
> > On Fri, May 2, 2025 at 4:39 PM Dan Carpenter <dan.carpenter@linaro.org> wrote:
> > >
> > > The "desc" variable is NULL and PTR_ERR(NULL) is zero/success.  Return
> > > a negative error code instead.
> > >
> > > Fixes: d2d10ede04b1 ("mtd: rawnand: Add Loongson-1 NAND Controller Driver")
> > > Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
> > > ---
> > > It's hard to know what the patch prefix should be here.  Ideally when we
> > > add a new driver we would use the patch prefix for the driver.
> > >
> > > Tired: subsystem: Add driver XXX
> > > Wired: subsystem: XXX: Add driver for XXX
> > >
> > >  drivers/mtd/nand/raw/loongson1-nand-controller.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/mtd/nand/raw/loongson1-nand-controller.c b/drivers/mtd/nand/raw/loongson1-nand-controller.c
> > > index 6a369b1c7d86..8754bb4f8b56 100644
> > > --- a/drivers/mtd/nand/raw/loongson1-nand-controller.c
> > > +++ b/drivers/mtd/nand/raw/loongson1-nand-controller.c
> > > @@ -371,7 +371,7 @@ static int ls1x_nand_dma_transfer(struct ls1x_nand_host *host, struct ls1x_nand_
> > >         desc = dmaengine_prep_slave_single(chan, dma_addr, op->len, xfer_dir, DMA_PREP_INTERRUPT);
> > >         if (!desc) {
> > >                 dev_err(dev, "failed to prepare DMA descriptor\n");
> > > -               ret = PTR_ERR(desc);
> > > +               ret = -ENOMEM;
> >
> > Thank you for fixing this issue.
> > However, I believe -EIO is more appropriate than -ENOMEM, since
> > dmaengine_prep_slave_single() can return errors other than -ENOMEM.
> >
>
> It's not an I/O error so -EIO isn't correct.
>
> There are a bunch of reasons it could fail but most likely
> dma_pool_alloc() failed.  I think -ENOMEM is correct.
>

Have you reviewed the implementation of ls1x_dma_prep_slave_sg()?
Errors in this function can be caused not only by -ENOMEM, but also by -EINVAL.
Moreover, in most cases, the error handling logic for
dmaengine_prep_slave_single() returns -EIO when the function returns
NULL.

> regards,
> dan carpenter
>


-- 
Best regards,

Keguang Zhang

Re: [PATCH next] mtd: rawnand: loongson1: Fix error code in ls1x_nand_dma_transfer()

[Dan Carpenter]

On Tue, May 06, 2025 at 06:01:15PM +0800, Keguang Zhang wrote:
> On Tue, May 6, 2025 at 5:32 PM Dan Carpenter <dan.carpenter@linaro.org> wrote:
> >
> > On Tue, May 06, 2025 at 05:16:03PM +0800, Keguang Zhang wrote:
> > > On Fri, May 2, 2025 at 4:39 PM Dan Carpenter <dan.carpenter@linaro.org> wrote:
> > > >
> > > > The "desc" variable is NULL and PTR_ERR(NULL) is zero/success.  Return
> > > > a negative error code instead.
> > > >
> > > > Fixes: d2d10ede04b1 ("mtd: rawnand: Add Loongson-1 NAND Controller Driver")
> > > > Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
> > > > ---
> > > > It's hard to know what the patch prefix should be here.  Ideally when we
> > > > add a new driver we would use the patch prefix for the driver.
> > > >
> > > > Tired: subsystem: Add driver XXX
> > > > Wired: subsystem: XXX: Add driver for XXX
> > > >
> > > >  drivers/mtd/nand/raw/loongson1-nand-controller.c | 2 +-
> > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > >
> > > > diff --git a/drivers/mtd/nand/raw/loongson1-nand-controller.c b/drivers/mtd/nand/raw/loongson1-nand-controller.c
> > > > index 6a369b1c7d86..8754bb4f8b56 100644
> > > > --- a/drivers/mtd/nand/raw/loongson1-nand-controller.c
> > > > +++ b/drivers/mtd/nand/raw/loongson1-nand-controller.c
> > > > @@ -371,7 +371,7 @@ static int ls1x_nand_dma_transfer(struct ls1x_nand_host *host, struct ls1x_nand_
> > > >         desc = dmaengine_prep_slave_single(chan, dma_addr, op->len, xfer_dir, DMA_PREP_INTERRUPT);
> > > >         if (!desc) {
> > > >                 dev_err(dev, "failed to prepare DMA descriptor\n");
> > > > -               ret = PTR_ERR(desc);
> > > > +               ret = -ENOMEM;
> > >
> > > Thank you for fixing this issue.
> > > However, I believe -EIO is more appropriate than -ENOMEM, since
> > > dmaengine_prep_slave_single() can return errors other than -ENOMEM.
> > >
> >
> > It's not an I/O error so -EIO isn't correct.
> >
> > There are a bunch of reasons it could fail but most likely
> > dma_pool_alloc() failed.  I think -ENOMEM is correct.
> >
> 
> Have you reviewed the implementation of ls1x_dma_prep_slave_sg()?

The ls1x_dma_prep_slave_sg() has basically two error cases, buggy drivers
and allocation errors.  Someone could argue that if people pass invalid
data then the correct return is -EINVAL but in these cases it's a buggy
driver and we fix bugs, we don't work around them.  So the correct
return is -ENOMEM.

> Errors in this function can be caused not only by -ENOMEM, but also by -EINVAL.
> Moreover, in most cases, the error handling logic for
> dmaengine_prep_slave_single() returns -EIO when the function returns
> NULL.

There are some that return -EIO but hardly the majority.  Other places
return -ENOMEM or -EINVAL.  It's not worth going back and fixing all of
these but really -ENOMEM is the correct return.

regards,
dan carpenter

Re: [PATCH next] mtd: rawnand: loongson1: Fix error code in ls1x_nand_dma_transfer()

[Keguang Zhang]

On Tue, May 6, 2025 at 7:16 PM Dan Carpenter <dan.carpenter@linaro.org> wrote:
>
> On Tue, May 06, 2025 at 06:01:15PM +0800, Keguang Zhang wrote:
> > On Tue, May 6, 2025 at 5:32 PM Dan Carpenter <dan.carpenter@linaro.org> wrote:
> > >
> > > On Tue, May 06, 2025 at 05:16:03PM +0800, Keguang Zhang wrote:
> > > > On Fri, May 2, 2025 at 4:39 PM Dan Carpenter <dan.carpenter@linaro.org> wrote:
> > > > >
> > > > > The "desc" variable is NULL and PTR_ERR(NULL) is zero/success.  Return
> > > > > a negative error code instead.
> > > > >
> > > > > Fixes: d2d10ede04b1 ("mtd: rawnand: Add Loongson-1 NAND Controller Driver")
> > > > > Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
> > > > > ---
> > > > > It's hard to know what the patch prefix should be here.  Ideally when we
> > > > > add a new driver we would use the patch prefix for the driver.
> > > > >
> > > > > Tired: subsystem: Add driver XXX
> > > > > Wired: subsystem: XXX: Add driver for XXX
> > > > >
> > > > >  drivers/mtd/nand/raw/loongson1-nand-controller.c | 2 +-
> > > > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > > > >
> > > > > diff --git a/drivers/mtd/nand/raw/loongson1-nand-controller.c b/drivers/mtd/nand/raw/loongson1-nand-controller.c
> > > > > index 6a369b1c7d86..8754bb4f8b56 100644
> > > > > --- a/drivers/mtd/nand/raw/loongson1-nand-controller.c
> > > > > +++ b/drivers/mtd/nand/raw/loongson1-nand-controller.c
> > > > > @@ -371,7 +371,7 @@ static int ls1x_nand_dma_transfer(struct ls1x_nand_host *host, struct ls1x_nand_
> > > > >         desc = dmaengine_prep_slave_single(chan, dma_addr, op->len, xfer_dir, DMA_PREP_INTERRUPT);
> > > > >         if (!desc) {
> > > > >                 dev_err(dev, "failed to prepare DMA descriptor\n");
> > > > > -               ret = PTR_ERR(desc);
> > > > > +               ret = -ENOMEM;
> > > >
> > > > Thank you for fixing this issue.
> > > > However, I believe -EIO is more appropriate than -ENOMEM, since
> > > > dmaengine_prep_slave_single() can return errors other than -ENOMEM.
> > > >
> > >
> > > It's not an I/O error so -EIO isn't correct.
> > >
> > > There are a bunch of reasons it could fail but most likely
> > > dma_pool_alloc() failed.  I think -ENOMEM is correct.
> > >
> >
> > Have you reviewed the implementation of ls1x_dma_prep_slave_sg()?
>
> The ls1x_dma_prep_slave_sg() has basically two error cases, buggy drivers
> and allocation errors.  Someone could argue that if people pass invalid
> data then the correct return is -EINVAL but in these cases it's a buggy
> driver and we fix bugs, we don't work around them.  So the correct
> return is -ENOMEM.
>

Yes, -EINVAL indicates a bug rather than a real error.
However, this assumes that the caller is aware they are providing invalid data.
Otherwise, they might be misled into thinking it is an out-of-memory
error (-ENOMEM).

> > Errors in this function can be caused not only by -ENOMEM, but also by -EINVAL.
> > Moreover, in most cases, the error handling logic for
> > dmaengine_prep_slave_single() returns -EIO when the function returns
> > NULL.
>
> There are some that return -EIO but hardly the majority.  Other places
> return -ENOMEM or -EINVAL.  It's not worth going back and fixing all of
> these but really -ENOMEM is the correct return.
>
> regards,
> dan carpenter
>

--
Best regards,

Keguang Zhang

Re: [PATCH next] mtd: rawnand: loongson1: Fix error code in ls1x_nand_dma_transfer()

[Miquel Raynal]

On Fri, 02 May 2025 11:39:29 +0300, Dan Carpenter wrote:
> The "desc" variable is NULL and PTR_ERR(NULL) is zero/success.  Return
> a negative error code instead.
> 
> 

Applied to nand/next, thanks!

[1/1] mtd: rawnand: loongson1: Fix error code in ls1x_nand_dma_transfer()
      commit: 0d470c72bea4d9f4c24b304fefdc857979cb5ca0

Patche(s) should be available on mtd/linux.git and will be
part of the next PR (provided that no robot complains by then).

Kind regards,
Miquèl