Re: [PATCH] media: nxp: imx8-isi: remove kzalloc_objs

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

On Thu, Mar 19, 2026 at 06:06:07PM -0700, Rosen Penev wrote:
> On Thu, Mar 19, 2026 at 5:57 PM Laurent Pinchart wrote:
> > On Thu, Mar 19, 2026 at 05:11:22PM -0700, Rosen Penev wrote:
> > > On Thu, Mar 19, 2026 at 3:09 PM Laurent Pinchart wrote:
> > > > On Thu, Mar 05, 2026 at 08:45:36PM -0800, Rosen Penev wrote:
> > > > > Use a flexible arraay member to combine allocations.
> > > > >
> > > > > It looks like pipes never gets freed anywhere. Meaning this effectively
> > > > > fixes a memory leak.
> > > > >
> > > > > Signed-off-by: Rosen Penev <rosenp@gmail.com>
> > > > > ---
> > > > >  drivers/media/platform/nxp/imx8-isi/imx8-isi-core.c | 11 ++++-------
> > > > >  drivers/media/platform/nxp/imx8-isi/imx8-isi-core.h |  3 ++-
> > > > >  2 files changed, 6 insertions(+), 8 deletions(-)
> > > > >
> > > > > diff --git a/drivers/media/platform/nxp/imx8-isi/imx8-isi-core.c b/drivers/media/platform/nxp/imx8-isi/imx8-isi-core.c
> > > > > index 16392420903a..657ffecc4d7e 100644
> > > > > --- a/drivers/media/platform/nxp/imx8-isi/imx8-isi-core.c
> > > > > +++ b/drivers/media/platform/nxp/imx8-isi/imx8-isi-core.c
> > > > > @@ -459,25 +459,21 @@ static const struct dev_pm_ops mxc_isi_pm_ops = {
> > > > >
> > > > >  static int mxc_isi_probe(struct platform_device *pdev)
> > > > >  {
> > > > > +     const struct mxc_isi_plat_data *pdata;
> > > > >       struct device *dev = &pdev->dev;
> > > > >       struct mxc_isi_dev *isi;
> > > > >       unsigned int dma_size;
> > > > >       unsigned int i;
> > > > >       int ret = 0;
> > > > >
> > > > > -     isi = devm_kzalloc(dev, sizeof(*isi), GFP_KERNEL);
> > > > > +     pdata = of_device_get_match_data(dev);
> > > > > +     isi = devm_kzalloc(dev, struct_size(isi, pipes, pdata->num_channels), GFP_KERNEL);
> > > > >       if (!isi)
> > > > >               return -ENOMEM;
> > > > >
> > > > >       isi->dev = dev;
> > > > >       platform_set_drvdata(pdev, isi);
> > > > >
> > > > > -     isi->pdata = of_device_get_match_data(dev);
> > > >
> > > > I'd keep
> > > >
> > > >         isi->pdata = pdata;
> > > >
> > > > here and not below.
> > >
> > > Sure
> > >
> > > > > -
> > > > > -     isi->pipes = kzalloc_objs(isi->pipes[0], isi->pdata->num_channels);
> > > >
> > > > Wouldn't it be simpler to just replace this with devm_kcalloc() ?
> > >
> > > That would only make sense if pipes remained a pointer. A flex array
> > > member allows combining allocations since it doesn't take up extra
> > > space.
> >
> > Yes, I understand that. My point was that with devm_kzalloc() here you
> > won't need to change the mxc_isi_dev structure. The leak fix will be a
> > one-liner patch.
> 
> Leak fix is not the point of the patch to be fair.

If I understand correctly, your main point is to combine two
allocations.

I don't liek this much in this specific case. mxc_isi_dev is the
top-level driver structure. As part of all the data it stores, there
is a pointer to a dynamically-allocated array, and the current
implementation happens to not have any other dynamically allocated
member. That is however not an intrinsic property of the mxc_isi_dev
structure. Treating pipes as a flex arrat within mxc_isi_dev won't scale
to a second similar member, and there's no reason to treat pipes in a
special way. I prefer fixing the leak and avoiding the flex array.

> > > Technically kzalloc_flex is simpler but I assume a devm version of
> > > that will be handled in another treewide commit.
> > > >
> > > >         isi->pipes = devm_kcalloc(dev, isi->pdata->num_channels,
> > > >                                   sizeof(isi->pipes[0]), GFP_KERNEL);
> > > >
> > > > No other change would be needed.
> > >
> > > With a flex array member, that's a compile time error, which I use as
> > > a hint to complete the conversion.
> > >
> > > > > -     if (!isi->pipes)
> > > > > -             return -ENOMEM;
> > > > > -
> > > > >       isi->num_clks = devm_clk_bulk_get_all(dev, &isi->clks);
> > > > >       if (isi->num_clks < 0)
> > > > >               return dev_err_probe(dev, isi->num_clks, "Failed to get clocks\n");
> > > > > @@ -487,6 +483,7 @@ static int mxc_isi_probe(struct platform_device *pdev)
> > > > >               return dev_err_probe(dev, PTR_ERR(isi->regs),
> > > > >                                    "Failed to get ISI register map\n");
> > > > >
> > > > > +     isi->pdata = pdata;
> > > > >       if (isi->pdata->gasket_ops) {
> > > > >               isi->gasket = syscon_regmap_lookup_by_phandle(dev->of_node,
> > > > >                                                             "fsl,blk-ctrl");
> > > > > diff --git a/drivers/media/platform/nxp/imx8-isi/imx8-isi-core.h b/drivers/media/platform/nxp/imx8-isi/imx8-isi-core.h
> > > > > index 3cbd35305af0..99532efa4e41 100644
> > > > > --- a/drivers/media/platform/nxp/imx8-isi/imx8-isi-core.h
> > > > > +++ b/drivers/media/platform/nxp/imx8-isi/imx8-isi-core.h
> > > > > @@ -286,7 +286,6 @@ struct mxc_isi_dev {
> > > > >       struct regmap                   *gasket;
> > > > >
> > > > >       struct mxc_isi_crossbar         crossbar;
> > > > > -     struct mxc_isi_pipe             *pipes;
> > > > >       struct mxc_isi_m2m              m2m;
> > > > >
> > > > >       struct media_device             media_dev;
> > > > > @@ -294,6 +293,8 @@ struct mxc_isi_dev {
> > > > >       struct v4l2_async_notifier      notifier;
> > > > >
> > > > >       struct dentry                   *debugfs_root;
> > > > > +
> > > > > +     struct mxc_isi_pipe             pipes[];
> > > > >  };
> > > > >
> > > > >  extern const struct mxc_gasket_ops mxc_imx8_gasket_ops;

-- 
Regards,

Laurent Pinchart