2021-05-19 17:38:57

by Dan Carpenter

Subject: [PATCH] drm/bridge: ti-sn65dsi86: fix a ternary type promotion bug

The ti_sn_aux_transfer() function returns ssize_t (signed long). It's
supposed to return negative error codes or the number of bytes
transferred. The "ret" variable is int and the "len" variable is
unsigned int.

The problem is that with a ternary like this, the negative int is first
type promoted to unsigned int to match "len" at this point it is a high
positive value. Then when it is type promoted to ssize_t (s64) it
remains a high positive value instead of sign extending and becoming a
negative again.

Fix this by removing the ternary.

Fixes: b137406d9679 ("drm/bridge: ti-sn65dsi86: If refclk, DP AUX can happen w/out pre-enable")
Signed-off-by: Dan Carpenter <[email protected]>
---
drivers/gpu/drm/bridge/ti-sn65dsi86.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi86.c b/drivers/gpu/drm/bridge/ti-sn65dsi86.c
index bb0a0e1c6341..45a2969afb2b 100644
--- a/drivers/gpu/drm/bridge/ti-sn65dsi86.c
+++ b/drivers/gpu/drm/bridge/ti-sn65dsi86.c
@@ -1042,7 +1042,9 @@ static ssize_t ti_sn_aux_transfer(struct drm_dp_aux *aux,
pm_runtime_mark_last_busy(pdata->dev);
pm_runtime_put_autosuspend(pdata->dev);

- return ret ? ret : len;
+ if (ret)
+ return ret;
+ return len;
}

static int ti_sn_bridge_parse_dsi_host(struct ti_sn65dsi86 *pdata)
--
2.30.2

2021-05-19 18:11:42

by Robert Foss

Subject: Re: [PATCH] drm/bridge: ti-sn65dsi86: fix a ternary type promotion bug

Since it fixes drm-misc-next, applied it there instead.

On Tue, 18 May 2021 at 15:20, Robert Foss <[email protected]> wrote:
>
> Hey Dan,
>
> Thanks for submitting this.
>
> On Tue, 18 May 2021 at 11:20, Dan Carpenter <[email protected]> wrote:
> >
> > The ti_sn_aux_transfer() function returns ssize_t (signed long). It's
> > supposed to return negative error codes or the number of bytes
> > transferred. The "ret" variable is int and the "len" variable is
> > unsigned int.
> >
> > The problem is that with a ternary like this, the negative int is first
> > type promoted to unsigned int to match "len" at this point it is a high
> > positive value. Then when it is type promoted to ssize_t (s64) it
> > remains a high positive value instead of sign extending and becoming a
> > negative again.
> >
> > Fix this by removing the ternary.
> >
> > Fixes: b137406d9679 ("drm/bridge: ti-sn65dsi86: If refclk, DP AUX can happen w/out pre-enable")
> > Signed-off-by: Dan Carpenter <[email protected]>
> > ---
> > drivers/gpu/drm/bridge/ti-sn65dsi86.c | 4 +++-
> > 1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi86.c b/drivers/gpu/drm/bridge/ti-sn65dsi86.c
> > index bb0a0e1c6341..45a2969afb2b 100644
> > --- a/drivers/gpu/drm/bridge/ti-sn65dsi86.c
> > +++ b/drivers/gpu/drm/bridge/ti-sn65dsi86.c
> > @@ -1042,7 +1042,9 @@ static ssize_t ti_sn_aux_transfer(struct drm_dp_aux *aux,
> > pm_runtime_mark_last_busy(pdata->dev);
> > pm_runtime_put_autosuspend(pdata->dev);
> >
> > - return ret ? ret : len;
> > + if (ret)
> > + return ret;
> > + return len;
> > }
> >
>
> Reviewed-by: Robert Foss <[email protected]>
>
> Applying to drm-misc-fixes.

2021-05-19 18:13:03

by Robert Foss

Subject: Re: [PATCH] drm/bridge: ti-sn65dsi86: fix a ternary type promotion bug

Hey Dan,

Thanks for submitting this.

On Tue, 18 May 2021 at 11:20, Dan Carpenter <[email protected]> wrote:
>
> The ti_sn_aux_transfer() function returns ssize_t (signed long). It's
> supposed to return negative error codes or the number of bytes
> transferred. The "ret" variable is int and the "len" variable is
> unsigned int.
>
> The problem is that with a ternary like this, the negative int is first
> type promoted to unsigned int to match "len" at this point it is a high
> positive value. Then when it is type promoted to ssize_t (s64) it
> remains a high positive value instead of sign extending and becoming a
> negative again.
>
> Fix this by removing the ternary.
>
> Fixes: b137406d9679 ("drm/bridge: ti-sn65dsi86: If refclk, DP AUX can happen w/out pre-enable")
> Signed-off-by: Dan Carpenter <[email protected]>
> ---
> drivers/gpu/drm/bridge/ti-sn65dsi86.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi86.c b/drivers/gpu/drm/bridge/ti-sn65dsi86.c
> index bb0a0e1c6341..45a2969afb2b 100644
> --- a/drivers/gpu/drm/bridge/ti-sn65dsi86.c
> +++ b/drivers/gpu/drm/bridge/ti-sn65dsi86.c
> @@ -1042,7 +1042,9 @@ static ssize_t ti_sn_aux_transfer(struct drm_dp_aux *aux,
> pm_runtime_mark_last_busy(pdata->dev);
> pm_runtime_put_autosuspend(pdata->dev);
>
> - return ret ? ret : len;
> + if (ret)
> + return ret;
> + return len;
> }
>

Reviewed-by: Robert Foss <[email protected]>

Applying to drm-misc-fixes.