Re: omapfb/dss: Delete an error message for a failed memory allocation in three functions

Ladislav Michl
2017-11-27T22:21:03Z

On Mon, Nov 27, 2017 at 08:22:51PM +0100, Ladislav Michl wrote:
> On Mon, Nov 27, 2017 at 07:12:50PM +0100, SF Markus Elfring wrote:
> > >> Can a default allocation failure report provide the information
> > >> which you might expect so far?
> > >
> > > You should be able to answer that question yourself.
> >
> > I can not answer this detail completely myself because my knowledge
> > is incomplete about your concrete expectations for the exception handling
> > which can lead to different views for the need of additional error messages.
>
> The rule is to be able to get idea what failed without recompiling kernel.
> If you think you can point to failed allocation with your changes, then
> you might be able to convice Andrew your change is an improvement.
>
> > > And if you are unable to do so, just do not sent changes pointed
> > > by any code analysis tools.
> >
> > They can point aspects out for further software development considerations,
> > can't they?
>
> So?
>
> > > As a side note, if you look at whole call chain, you'll find quite some
> > > room for optimizations - look how dev and pdev are used. That also applies
> > > to other patches.
> >
> > Would you prefer to improve the source code in other ways?
>
> I would prefer you to look at code as a whole, not as an isolated set
> of lines which can be changes to shut up some random warning obtained
> from code analysis tool.
>
> Behold, here we saved over 100 bytes just by minor clean up. Patch
> is a mess, should be probably polished and splitted, but you'll get
> an idea. That said, we saved more than by deleting one error message
> and if you can prove we will not loose information _what_ failed
> with your patch, we can save even more.

Well, if we remove allocation, we do not need to print error message...
And numbers are even better.

> text data bss dec hex filename
> 59319 2372 4184 65875 10153 dispc.o.orig
> 59178 2372 4184 65734 100c6 dispc.o
59095 2372 4184 65651 10073 dispc.o.noalloc

Care to test this? It is a mess of unrelated changes, but I'm just
interested if it works...

diff --git a/drivers/video/fbdev/omap2/omapfb/dss/dispc.c b/drivers/video/fbdev/omap2/omapfb/dss/dispc.c
index 7a75dfda9845..f6d631a68c70 100644
--- a/drivers/video/fbdev/omap2/omapfb/dss/dispc.c
+++ b/drivers/video/fbdev/omap2/omapfb/dss/dispc.c
@@ -3976,52 +3976,33 @@ static const struct dispc_features omap54xx_dispc_feats = {
.has_writeback = true,
};

-static int dispc_init_features(struct platform_device *pdev)
+static const struct dispc_features* dispc_get_features(void)
{
- const struct dispc_features *src;
- struct dispc_features *dst;
-
- dst = devm_kzalloc(&pdev->dev, sizeof(*dst), GFP_KERNEL);
- if (!dst) {
- dev_err(&pdev->dev, "Failed to allocate DISPC Features\n");
- return -ENOMEM;
- }
-
switch (omapdss_get_version()) {
case OMAPDSS_VER_OMAP24xx:
- src = &omap24xx_dispc_feats;
- break;
+ return &omap24xx_dispc_feats;

case OMAPDSS_VER_OMAP34xx_ES1:
- src = &omap34xx_rev1_0_dispc_feats;
- break;
+ return &omap34xx_rev1_0_dispc_feats;

case OMAPDSS_VER_OMAP34xx_ES3:
case OMAPDSS_VER_OMAP3630:
case OMAPDSS_VER_AM35xx:
case OMAPDSS_VER_AM43xx:
- src = &omap34xx_rev3_0_dispc_feats;
- break;
+ return &omap34xx_rev3_0_dispc_feats;

case OMAPDSS_VER_OMAP4430_ES1:
case OMAPDSS_VER_OMAP4430_ES2:
case OMAPDSS_VER_OMAP4:
- src = &omap44xx_dispc_feats;
- break;
+ return &omap44xx_dispc_feats;

case OMAPDSS_VER_OMAP5:
case OMAPDSS_VER_DRA7xx:
- src = &omap54xx_dispc_feats;
- break;
+ return &omap54xx_dispc_feats;

default:
- return -ENODEV;
+ return NULL;
}
-
- memcpy(dst, src, sizeof(*dst));
- dispc.feat = dst;
-
- return 0;
}

static irqreturn_t dispc_irq_handler(int irq, void *arg)
@@ -4068,54 +4049,53 @@ EXPORT_SYMBOL(dispc_free_irq);
/* DISPC HW IP initialisation */
static int dispc_bind(struct device *dev, struct device *master, void *data)
{
- struct platform_device *pdev = to_platform_device(dev);
u32 rev;
int r = 0;
struct resource *dispc_mem;
- struct device_node *np = pdev->dev.of_node;
+ struct device_node *np = dev->of_node;

- dispc.pdev = pdev;
+ dispc.pdev = to_platform_device(dev);

spin_lock_init(&dispc.control_lock);

- r = dispc_init_features(dispc.pdev);
- if (r)
- return r;
+ dispc.feat = dispc_get_features();
+ if (dispc.feat)
+ return -ENODEV;

dispc_mem = platform_get_resource(dispc.pdev, IORESOURCE_MEM, 0);
if (!dispc_mem) {
- DSSERR("can't get IORESOURCE_MEM DISPC\n");
+ dev_err(dev, "can't get IORESOURCE_MEM DISPC\n");
return -EINVAL;
}

- dispc.base = devm_ioremap(&pdev->dev, dispc_mem->start,
+ dispc.base = devm_ioremap(dev, dispc_mem->start,
resource_size(dispc_mem));
if (!dispc.base) {
- DSSERR("can't ioremap DISPC\n");
+ dev_err(dev, "can't ioremap DISPC\n");
return -ENOMEM;
}

dispc.irq = platform_get_irq(dispc.pdev, 0);
if (dispc.irq < 0) {
- DSSERR("platform_get_irq failed\n");
+ dev_err(dev, "platform_get_irq failed\n");
return -ENODEV;
}

if (np && of_property_read_bool(np, "syscon-pol")) {
dispc.syscon_pol = syscon_regmap_lookup_by_phandle(np, "syscon-pol");
if (IS_ERR(dispc.syscon_pol)) {
- dev_err(&pdev->dev, "failed to get syscon-pol regmap\n");
+ dev_err(dev, "failed to get syscon-pol regmap\n");
return PTR_ERR(dispc.syscon_pol);
}

if (of_property_read_u32_index(np, "syscon-pol", 1,
&dispc.syscon_pol_offset)) {
- dev_err(&pdev->dev, "failed to get syscon-pol offset\n");
+ dev_err(dev, "failed to get syscon-pol offset\n");
return -EINVAL;
}
}

- pm_runtime_enable(&pdev->dev);
+ pm_runtime_enable(dev);

r = dispc_runtime_get();
if (r)
@@ -4124,7 +4104,7 @@ static int dispc_bind(struct device *dev, struct device *master, void *data)
_omap_dispc_initial_config();

rev = dispc_read_reg(DISPC_REVISION);
- dev_dbg(&pdev->dev, "OMAP DISPC rev %d.%d\n",
+ dev_dbg(dev, "OMAP DISPC rev %d.%d\n",
FLD_GET(rev, 7, 4), FLD_GET(rev, 3, 0));

dispc_runtime_put();
@@ -4136,7 +4116,7 @@ static int dispc_bind(struct device *dev, struct device *master, void *data)
return 0;

err_runtime_get:
- pm_runtime_disable(&pdev->dev);
+ pm_runtime_disable(dev);
return r;
}