Re: [PATCH v2 2/5] iommu/mediatek: Add error path for loop of mm_dts_parse

From: Robin Murphy
Date: Thu Jun 23 2022 - 06:08:48 EST


On 2022-06-23 02:54, Yong Wu wrote:
On Thu, 2022-06-16 at 11:31 +0100, Robin Murphy wrote:
On 2022-06-16 11:08, Yong Wu wrote:
On Thu, 2022-06-16 at 09:59 +0100, Robin Murphy wrote:
On 2022-06-16 06:42, Yong Wu wrote:
The mtk_iommu_mm_dts_parse will parse the smi larbs nodes. if
the
i+1
larb is parsed fail(return -EINVAL), we should of_node_put for
the
0..i
larbs. In the fail path, one of_node_put matches with
of_parse_phandle in
it.

Fixes: d2e9a1102cfc ("iommu/mediatek: Contain MM IOMMU flow
with
the MM TYPE")
Signed-off-by: Yong Wu <yong.wu@xxxxxxxxxxxx>
---
drivers/iommu/mtk_iommu.c | 21 ++++++++++++++++-----
1 file changed, 16 insertions(+), 5 deletions(-)

[snip..]

+err_larbnode_put:
+ while (i--) {
+ larbnode = of_parse_phandle(dev->of_node,
"mediatek,larbs", i);
+ if (larbnode &&
of_device_is_available(larbnode)) {
+ of_node_put(larbnode);
+ of_node_put(larbnode);
+ }

This looks a bit awkward - could we not just iterate through
data->larb_imu and put dev->of_node for each valid dev?

It should work. Thanks very much.


Also, of_find_device_by_node() takes a reference on the struct
device
itself, so strictly we should be doing put_device() on those as
well
if we're bailing out.

Thanks for this hint. A new reference for me. I will add it.

In fact, thinking about it some more we may as well do the
of_node_put()
unconditionally immediately after the of_find_device_by_node() call,

of_node_put is called in component_release_of in the normal case, thus
we shouldn't call of_node_put unconditionally. Right?

As it stands, yes. However I'm also figuring that we could just use component_match_add() there, and probably also switch to component_compare_dev as the the comparison, since we've already resolved the larb device, and it is the device itself that we're interested in here, rather than just its of_node.

I *think* this idea could end up with simpler code overall, but as always, feel free to ignore the suggestion if you think it wouldn't make enough difference to be worth the bother.

Thanks,
Robin.