在 2025/2/10 18:03, Laurent Pinchart 写道:
Hi Zekun,
On Mon, Feb 10, 2025 at 02:47:28PM +0800, zhangzekun (A) wrote:
I think we all agree that of_find_node_by_name() is miused, and that it
shows the API isn't optimal. What we have different opinions on is how
to make the API less error-prone. I think adding a new
of_find_node_by_name_balanced() function works around the issue and
doesn't improve the situation much, I would argue it makes things even
more confusing.
We have only 20 calls to of_find_node_by_name() with a non-NULL first
argument in v6.14-rc1:
arch/powerpc/platforms/chrp/pci.c: rtas = of_find_node_by_name (root, "rtas");
The 'root' variable here is the result of a call to
'of_find_node_by_path("/")', so I think we could pass a null pointer
instead to simplify things.
arch/powerpc/platforms/powermac/pic.c: slave = of_find_node_by_name(master, "mac-io");
Here I believe of_find_node_by_name() is called to find a *child* node
of 'master'. of_find_node_by_name() is the wrong function for that.
arch/sparc/kernel/leon_kernel.c: np = of_find_node_by_name(rootnp, "GAISLER_IRQMP");
arch/sparc/kernel/leon_kernel.c: np = of_find_node_by_name(rootnp, "01_00d");
arch/sparc/kernel/leon_kernel.c: np = of_find_node_by_name(nnp, "GAISLER_GPTIMER");
arch/sparc/kernel/leon_kernel.c: np = of_find_node_by_name(nnp, "01_011");
Here too the code seems to be looking for child nodes only (but I
couldn't find a DT example or binding in-tree, so I'm not entirely
sure).
drivers/clk/ti/clk.c: return of_find_node_by_name(from, tmp);
Usage here seems correct, the reference-count decrement is intended.
drivers/media/i2c/max9286.c: i2c_mux = of_find_node_by_name(dev->of_node, "i2c-mux");
drivers/media/platform/qcom/venus/core.c: enp = of_find_node_by_name(dev->of_node, node_name);
drivers/net/dsa/bcm_sf2.c: ports = of_find_node_by_name(dn, "ports");
drivers/net/dsa/hirschmann/hellcreek_ptp.c: leds = of_find_node_by_name(hellcreek->dev->of_node, "leds");
drivers/net/ethernet/broadcom/asp2/bcmasp.c: ports_node = of_find_node_by_name(dev->of_node, "ethernet-ports");
drivers/net/ethernet/marvell/prestera/prestera_main.c: ports = of_find_node_by_name(sw->np, "ports");
drivers/net/pse-pd/tps23881.c: channels_node = of_find_node_by_name(priv->np, "channels");
drivers/regulator/scmi-regulator.c: np = of_find_node_by_name(handle->dev->of_node, "regulators");
drivers/regulator/tps6594-regulator.c: np = of_find_node_by_name(tps->dev->of_node, multi_regs[multi].supply_name);
Incorrect usage, as far as I understand all those drivers are looking
for child nodes only.
drivers/of/unittest.c: found = of_find_node_by_name(nd->overlay, "test-unittest16");
drivers/of/unittest.c: found = of_find_node_by_name(nd->overlay, "test-unittest17");
drivers/of/unittest.c: found = of_find_node_by_name(nd->overlay, "test-unittest18");
drivers/of/unittest.c: found = of_find_node_by_name(nd->overlay, "test-unittest19");
Here too I think only child nodes are meant to be considered.
of_find_node_by_name() is very much misused as most callers want to find
child nodes, while of_find_node_by_name() will walk the whole DT from a
given starting point.
I think the right fix here is to
- Replace of_find_node_by_name(root, ...) with
of_find_node_by_name(NULL, ...) in arch/powerpc/platforms/chrp/pci.c
(if my understanding of the code is correct).
For arch/powerpc/platforms/chrp/pci.c, noticing that there is a comment
in setup_peg2():
/* keep the reference to the root node */
It might can not be convert to of_find_node_by_name(NULL, ...), and the
origin use of of_find_node_by_name() put the ref count which want to be
kept.
But the reference is dropped by of_find_node_by_name(). Unless I'm
missing something, dropping the lien
struct device_node *root = of_find_node_by_path("/");
and changing
rtas = of_find_node_by_name (root, "rtas");
to
rtas = of_find_node_by_name (NULL, "rtas");
will not change the behaviour of the code.
Hi, Laurent,
I think that the original code try to keep the refcount get by
of_find_node_by_path(), but leak it accidently by
of_find_node_by_name(). I am not sure that what driver really wants to
do and if it has a bug here.
Beset Regards,
Zekun
