Add a new function to get an IIO backend by its index in the
io-backends device tree property. This is useful for multi-channel
devices that have multiple backends, where looking up by index is
more straightforward than using named backends.
The new function directly uses the index to find the backend reference
in the io-backends property, avoiding the need for io-backend-names.
Reviewed-by: Nuno Sá <nuno.sa@analog.com>
Signed-off-by: Antoniu Miclaus <antoniu.miclaus@analog.com>
---
Changes in v4:
- Add Reviewed-by from Nuno Sá
drivers/iio/industrialio-backend.c | 61 ++++++++++++++++++++----------
include/linux/iio/backend.h | 2 +
2 files changed, 44 insertions(+), 19 deletions(-)
diff --git a/drivers/iio/industrialio-backend.c b/drivers/iio/industrialio-backend.c
index 447b694d6d5f..d90a3a0b17c6 100644
--- a/drivers/iio/industrialio-backend.c
+++ b/drivers/iio/industrialio-backend.c
@@ -949,25 +949,16 @@ int iio_backend_data_transfer_addr(struct iio_backend *back, u32 address)
}
EXPORT_SYMBOL_NS_GPL(iio_backend_data_transfer_addr, "IIO_BACKEND");
-static struct iio_backend *__devm_iio_backend_fwnode_get(struct device *dev, const char *name,
- struct fwnode_handle *fwnode)
+static struct iio_backend *
+__devm_iio_backend_fwnode_get_by_index(struct device *dev,
+ struct fwnode_handle *fwnode,
+ unsigned int index)
{
- struct fwnode_handle *fwnode_back;
+ struct fwnode_handle *fwnode_back __free(fwnode_handle) =
+ fwnode_find_reference(fwnode, "io-backends", index);
struct iio_backend *back;
- unsigned int index;
int ret;
- if (name) {
- ret = device_property_match_string(dev, "io-backend-names",
- name);
- if (ret < 0)
- return ERR_PTR(ret);
- index = ret;
- } else {
- index = 0;
- }
-
- fwnode_back = fwnode_find_reference(fwnode, "io-backends", index);
if (IS_ERR(fwnode_back))
return dev_err_cast_probe(dev, fwnode_back,
"Cannot get Firmware reference\n");
@@ -977,21 +968,35 @@ static struct iio_backend *__devm_iio_backend_fwnode_get(struct device *dev, con
if (!device_match_fwnode(back->dev, fwnode_back))
continue;
- fwnode_handle_put(fwnode_back);
ret = __devm_iio_backend_get(dev, back);
if (ret)
return ERR_PTR(ret);
- if (name)
- back->idx = index;
+ back->idx = index;
return back;
}
- fwnode_handle_put(fwnode_back);
return ERR_PTR(-EPROBE_DEFER);
}
+static struct iio_backend *__devm_iio_backend_fwnode_get(struct device *dev, const char *name,
+ struct fwnode_handle *fwnode)
+{
+ unsigned int index = 0;
+ int ret;
+
+ if (name) {
+ ret = device_property_match_string(dev, "io-backend-names",
+ name);
+ if (ret < 0)
+ return ERR_PTR(ret);
+ index = ret;
+ }
+
+ return __devm_iio_backend_fwnode_get_by_index(dev, fwnode, index);
+}
+
/**
* devm_iio_backend_get - Device managed backend device get
* @dev: Consumer device for the backend
@@ -1008,6 +1013,24 @@ struct iio_backend *devm_iio_backend_get(struct device *dev, const char *name)
}
EXPORT_SYMBOL_NS_GPL(devm_iio_backend_get, "IIO_BACKEND");
+/**
+ * devm_iio_backend_get_by_index - Device managed backend device get by index
+ * @dev: Consumer device for the backend
+ * @index: Index of the backend in the io-backends property
+ *
+ * Get's the backend at @index associated with @dev.
+ *
+ * RETURNS:
+ * A backend pointer, negative error pointer otherwise.
+ */
+struct iio_backend *devm_iio_backend_get_by_index(struct device *dev,
+ unsigned int index)
+{
+ return __devm_iio_backend_fwnode_get_by_index(dev, dev_fwnode(dev),
+ index);
+}
+EXPORT_SYMBOL_NS_GPL(devm_iio_backend_get_by_index, "IIO_BACKEND");
+
/**
* devm_iio_backend_fwnode_get - Device managed backend firmware node get
* @dev: Consumer device for the backend
diff --git a/include/linux/iio/backend.h b/include/linux/iio/backend.h
index 7f815f3fed6a..8f18df0ca896 100644
--- a/include/linux/iio/backend.h
+++ b/include/linux/iio/backend.h
@@ -237,6 +237,8 @@ int iio_backend_extend_chan_spec(struct iio_backend *back,
struct iio_chan_spec *chan);
void *iio_backend_get_priv(const struct iio_backend *conv);
struct iio_backend *devm_iio_backend_get(struct device *dev, const char *name);
+struct iio_backend *devm_iio_backend_get_by_index(struct device *dev,
+ unsigned int index);
struct iio_backend *devm_iio_backend_fwnode_get(struct device *dev,
const char *name,
struct fwnode_handle *fwnode);
--
2.43.0
On Mon, 23 Feb 2026 18:21:02 +0200
Antoniu Miclaus <antoniu.miclaus@analog.com> wrote:
> Add a new function to get an IIO backend by its index in the
> io-backends device tree property. This is useful for multi-channel
> devices that have multiple backends, where looking up by index is
> more straightforward than using named backends.
>
> The new function directly uses the index to find the backend reference
> in the io-backends property, avoiding the need for io-backend-names.
>
> Reviewed-by: Nuno Sá <nuno.sa@analog.com>
> Signed-off-by: Antoniu Miclaus <antoniu.miclaus@analog.com>
Hi Antoniu,
I'm seeing the use of __free as an unrelated change that I'd prefer
to see as a precusor cleanup patch.
Thanks,
Jonathan
> ---
> Changes in v4:
> - Add Reviewed-by from Nuno Sá
>
> drivers/iio/industrialio-backend.c | 61 ++++++++++++++++++++----------
> include/linux/iio/backend.h | 2 +
> 2 files changed, 44 insertions(+), 19 deletions(-)
>
> diff --git a/drivers/iio/industrialio-backend.c b/drivers/iio/industrialio-backend.c
> index 447b694d6d5f..d90a3a0b17c6 100644
> --- a/drivers/iio/industrialio-backend.c
> +++ b/drivers/iio/industrialio-backend.c
> @@ -949,25 +949,16 @@ int iio_backend_data_transfer_addr(struct iio_backend *back, u32 address)
> }
> EXPORT_SYMBOL_NS_GPL(iio_backend_data_transfer_addr, "IIO_BACKEND");
>
> -static struct iio_backend *__devm_iio_backend_fwnode_get(struct device *dev, const char *name,
> - struct fwnode_handle *fwnode)
> +static struct iio_backend *
> +__devm_iio_backend_fwnode_get_by_index(struct device *dev,
> + struct fwnode_handle *fwnode,
> + unsigned int index)
> {
> - struct fwnode_handle *fwnode_back;
> + struct fwnode_handle *fwnode_back __free(fwnode_handle) =
> + fwnode_find_reference(fwnode, "io-backends", index);
This use of __free is a refactor, that you are doing whilst you happen to be here.
Really should be in a separate precursor patch so that we can more
easily see what the real code movement going on here is about.
> struct iio_backend *back;
> - unsigned int index;
> int ret;
>
> - if (name) {
> - ret = device_property_match_string(dev, "io-backend-names",
> - name);
> - if (ret < 0)
> - return ERR_PTR(ret);
> - index = ret;
> - } else {
> - index = 0;
> - }
> -
> - fwnode_back = fwnode_find_reference(fwnode, "io-backends", index);
> if (IS_ERR(fwnode_back))
> return dev_err_cast_probe(dev, fwnode_back,
> "Cannot get Firmware reference\n");
> @@ -977,21 +968,35 @@ static struct iio_backend *__devm_iio_backend_fwnode_get(struct device *dev, con
> if (!device_match_fwnode(back->dev, fwnode_back))
> continue;
>
> - fwnode_handle_put(fwnode_back);
> ret = __devm_iio_backend_get(dev, back);
> if (ret)
> return ERR_PTR(ret);
>
> - if (name)
> - back->idx = index;
> + back->idx = index;
>
> return back;
> }
>
> - fwnode_handle_put(fwnode_back);
> return ERR_PTR(-EPROBE_DEFER);
> }
>
> +static struct iio_backend *__devm_iio_backend_fwnode_get(struct device *dev, const char *name,
> + struct fwnode_handle *fwnode)
> +{
> + unsigned int index = 0;
> + int ret;
> +
> + if (name) {
> + ret = device_property_match_string(dev, "io-backend-names",
> + name);
> + if (ret < 0)
> + return ERR_PTR(ret);
> + index = ret;
> + }
> +
> + return __devm_iio_backend_fwnode_get_by_index(dev, fwnode, index);
> +}
> +
> /**
> * devm_iio_backend_get - Device managed backend device get
> * @dev: Consumer device for the backend
> @@ -1008,6 +1013,24 @@ struct iio_backend *devm_iio_backend_get(struct device *dev, const char *name)
> }
> EXPORT_SYMBOL_NS_GPL(devm_iio_backend_get, "IIO_BACKEND");
>
> +/**
> + * devm_iio_backend_get_by_index - Device managed backend device get by index
> + * @dev: Consumer device for the backend
> + * @index: Index of the backend in the io-backends property
> + *
> + * Get's the backend at @index associated with @dev.
Gets
It could either be
Get us (in which case our Get's is valid) or Gets as it the function is
responsible for getting. I think Gets is more natural here.
> + *
> + * RETURNS:
> + * A backend pointer, negative error pointer otherwise.
> + */
> +struct iio_backend *devm_iio_backend_get_by_index(struct device *dev,
> + unsigned int index)
> +{
> + return __devm_iio_backend_fwnode_get_by_index(dev, dev_fwnode(dev),
> + index);
> +}
> +EXPORT_SYMBOL_NS_GPL(devm_iio_backend_get_by_index, "IIO_BACKEND");
> +
> /**
> * devm_iio_backend_fwnode_get - Device managed backend firmware node get
> * @dev: Consumer device for the backend
> diff --git a/include/linux/iio/backend.h b/include/linux/iio/backend.h
> index 7f815f3fed6a..8f18df0ca896 100644
> --- a/include/linux/iio/backend.h
> +++ b/include/linux/iio/backend.h
> @@ -237,6 +237,8 @@ int iio_backend_extend_chan_spec(struct iio_backend *back,
> struct iio_chan_spec *chan);
> void *iio_backend_get_priv(const struct iio_backend *conv);
> struct iio_backend *devm_iio_backend_get(struct device *dev, const char *name);
> +struct iio_backend *devm_iio_backend_get_by_index(struct device *dev,
> + unsigned int index);
> struct iio_backend *devm_iio_backend_fwnode_get(struct device *dev,
> const char *name,
> struct fwnode_handle *fwnode);
On Mon, Feb 23, 2026 at 06:21:02PM +0200, Antoniu Miclaus wrote:
> Add a new function to get an IIO backend by its index in the
> io-backends device tree property. This is useful for multi-channel
> devices that have multiple backends, where looking up by index is
> more straightforward than using named backends.
>
> The new function directly uses the index to find the backend reference
> in the io-backends property, avoiding the need for io-backend-names.
...
> +static struct iio_backend *
> +__devm_iio_backend_fwnode_get_by_index(struct device *dev,
> + struct fwnode_handle *fwnode,
> + unsigned int index)
> {
> + struct fwnode_handle *fwnode_back __free(fwnode_handle) =
> + fwnode_find_reference(fwnode, "io-backends", index);
Better for maintenance to have this near to the check.
It will narrow down the scope as required, in case more code appear in between.
> struct iio_backend *back;
> int ret;
>
(yes, the above blank line is fine)
struct fwnode_handle *fwnode_back __free(fwnode_handle) =
fwnode_find_reference(fwnode, "io-backends", index);
> if (IS_ERR(fwnode_back))
> return dev_err_cast_probe(dev, fwnode_back,
> "Cannot get Firmware reference\n");
> if (!device_match_fwnode(back->dev, fwnode_back))
> continue;
>
> - fwnode_handle_put(fwnode_back);
> ret = __devm_iio_backend_get(dev, back);
> if (ret)
> return ERR_PTR(ret);
>
> - if (name)
> - back->idx = index;
> + back->idx = index;
>
> return back;
> }
>
> - fwnode_handle_put(fwnode_back);
> return ERR_PTR(-EPROBE_DEFER);
> }
...
> +static struct iio_backend *__devm_iio_backend_fwnode_get(struct device *dev, const char *name,
> + struct fwnode_handle *fwnode)
> +{
> + unsigned int index = 0;
Better to maintain when assignment is closer to the real use. See below.
> + int ret;
> +
> + if (name) {
> + ret = device_property_match_string(dev, "io-backend-names",
> + name);
This can be located on a single line (it's only 82 characters long).
> + if (ret < 0)
> + return ERR_PTR(ret);
> + index = ret;
} else {
index = 0;
> + }
> +
> + return __devm_iio_backend_fwnode_get_by_index(dev, fwnode, index);
> +}
--
With Best Regards,
Andy Shevchenko
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