Re: [RFC] i2c-stub: make it usable with DT when booting
Hi Jean, > I get the idea and I understand the need to emulate the devices early > in the boot process. However, how do you deal with the I2C devices > pre-initialization (setting initial register values)? This is typically > done in user-space with the i2c-stub-from-dump script, or manual calls > to i2cset, but that would be too late in your case, wouldn't it? Yes. In my case, all 0 memory is fine. I needed to check writes which were enabling "channels" allowing me to do further initialization. I see the point, though, that we likely want to address your question before going upstream. > Code looks sane, but I can't comment on the bindings side of things as > this isn't my area. Sure, thanks for checking the code! Regards, Wolfram signature.asc Description: PGP signature
Re: [RFC] i2c-stub: make it usable with DT when booting
Hi Wolfram,
On Tue, 16 May 2017 13:27:58 +0200, Wolfram Sang wrote:
> This patch makes the stub driver parse the device tree when booting and
> create a virtual bus with the desired devices attached. Here is an
> example DTS snipplet making use of it. It is for simulating a more
> complex camera device which has dependencies which needs to be sorted
> out at boot time:
>
> i2c@42 {
> compatible = "i2c-stub";
>
> #address-cells = <1>;
> #size-cells = <0>;
>
> des@4c {
> compatible = "maxim,max9268";
> reg = <0x4c>;
> };
>
> eeprom@57 {
> compatible = "atmel,24c02";
> reg = <0x57>;
> };
> };
I get the idea and I understand the need to emulate the devices early
in the boot process. However, how do you deal with the I2C devices
pre-initialization (setting initial register values)? This is typically
done in user-space with the i2c-stub-from-dump script, or manual calls
to i2cset, but that would be too late in your case, wouldn't it?
>
> FIXME: can fw_* calls be used instead of of_*?
>
> Signed-off-by: Wolfram Sang
> ---
>
> It was really useful when developing. When using fw_* calls, we probably could
> make use of it with ACPI as well. Still, calling for opinions if we want this
> upstream or if we want to stay module-only? Also, the binding should really
> be marked as "development only". Or is it better to keep it as a separate
> patch to keep the binding un-official?
Code looks sane, but I can't comment on the bindings side of things as
this isn't my area.
--
Jean Delvare
SUSE L3 Support
[RFC] i2c-stub: make it usable with DT when booting
This patch makes the stub driver parse the device tree when booting and
create a virtual bus with the desired devices attached. Here is an
example DTS snipplet making use of it. It is for simulating a more
complex camera device which has dependencies which needs to be sorted
out at boot time:
i2c@42 {
compatible = "i2c-stub";
#address-cells = <1>;
#size-cells = <0>;
des@4c {
compatible = "maxim,max9268";
reg = <0x4c>;
};
eeprom@57 {
compatible = "atmel,24c02";
reg = <0x57>;
};
};
FIXME: can fw_* calls be used instead of of_*?
Signed-off-by: Wolfram Sang
---
It was really useful when developing. When using fw_* calls, we probably could
make use of it with ACPI as well. Still, calling for opinions if we want this
upstream or if we want to stay module-only? Also, the binding should really
be marked as "development only". Or is it better to keep it as a separate
patch to keep the binding un-official?
drivers/i2c/Kconfig| 2 +-
drivers/i2c/i2c-stub.c | 34 ++
2 files changed, 35 insertions(+), 1 deletion(-)
diff --git a/drivers/i2c/Kconfig b/drivers/i2c/Kconfig
index efc3354d60ae89..6d38b38632f44c 100644
--- a/drivers/i2c/Kconfig
+++ b/drivers/i2c/Kconfig
@@ -99,7 +99,7 @@ source drivers/i2c/busses/Kconfig
config I2C_STUB
tristate "I2C/SMBus Test Stub"
- depends on m
+ depends on m || OF
default 'n'
help
This module may be useful to developers of SMBus client drivers,
diff --git a/drivers/i2c/i2c-stub.c b/drivers/i2c/i2c-stub.c
index 5627b1df391c7e..ce30bc4ac15a28 100644
--- a/drivers/i2c/i2c-stub.c
+++ b/drivers/i2c/i2c-stub.c
@@ -359,10 +359,44 @@ static void i2c_stub_free(void)
kfree(stub_chips);
}
+#ifdef CONFIG_OF
+void i2c_stub_parse_of(void)
+{
+ struct device_node *np, *child;
+ u32 reg, i = 0;
+
+ np = of_find_compatible_node(NULL, NULL, "i2c-stub");
+ if (!np)
+ return;
+
+ for_each_available_child_of_node(np, child) {
+ if (of_property_read_u32(child, "reg", ) == 0) {
+ chip_addr[i++] = reg;
+ if (i == MAX_CHIPS) {
+ pr_warn("Maximum number of chips reached!\n");
+ break;
+ }
+ }
+ }
+
+ stub_adapter.dev.of_node = np;
+
+ np = of_find_compatible_node(np, NULL, "i2c-stub");
+ if (np) {
+ pr_warn("Driver can currently do only one stub from DT!\n");
+ of_node_put(np);
+ }
+}
+#else
+void i2c_stub_parse_of(void) { }
+#endif
+
static int __init i2c_stub_init(void)
{
int i, ret;
+ i2c_stub_parse_of();
+
if (!chip_addr[0]) {
pr_err("Please specify a chip address\n");
return -ENODEV;
--
2.11.0
