Device-Tree compact API
------------------------
Common code seen in driver’s probe reads device tree values and handling
erroneous return codes from all those of_property_read_xxx() APIs. This
common code is factored out by the of_property_map module which allows
driver’s probe to replace that (often lengthy) code with a concise table:
struct of_prop_map map[] = {
{"i2c", &dev->id, OF_REQ, OF_ID, -1},
{"qcom,clk-freq-out", &dev->clk_freq_out, OF_REQ, OF_U32, 0},
{"qcom,clk-freq-in", &dev->clk_freq_in, OF_REQ, OF_U32, 0},
{"qcom,disable-dma", &dev->disable_dma, OF_OPT, OF_BOOL, 0},
{"qcom,master-id", &dev->mstr_id, OF_SGST, OF_U32, 0},
{NULL, NULL, 0, 0, 0},
};
Then call populate to read the values into the device’s variables:
ret = of_prop_populate(dev, dev->of_node, map);
An equivalent code snippet using the traditional of_property_read_XXXX()
API. Note that the equivalent is longer and more difficult to follow and
debug:
/* optional property */
dev->disable_dma = of_property_read_bool(node, "qcom,disable-dma");
ret = of_property_read_u32(dev->node, "qcom,clk-freq-out", &dev->clk_freq_out);
if (ret) {
dev_err(dev, "error: missing 'qcom,clk-freq-out' DT property\n");
if (!err)
err = ret;
}
ret = of_property_read_u32(dev->node, "qcom,clk-freq-in", &dev->clk_freq_in);
if (ret) {
dev_err(dev, "error: missing 'qcom,clk-freq-in' DT property\n");
if (!err)
err = ret;
}
/* suggested property */
ret = of_property_read_u32(dev->node, "qcom,master-id", &dev->mstr_id);
if (ret && !err)
err = ret;
ret = of_alias_get_id(dev->node, "i2c");
if (ret < 0) {
dev_err(dev, "error: missing '"i2c"' DT property\n");
if (!err)
err = ret;
} else {
dev->id = ret;
}
The Device-Tree node and alias which are read by the above code snippets:
aliases {
i2c0 = &i2c_0; /* I2C0 controller device */
};
i2c_0: i2c@78b6000 { /* BLSP1 QUP2 */
compatible = "qcom,i2c-msm-v2";
reg-names = "qup_phys_addr", "bam_phys_addr";
reg = <0x78b6000 0x600>,
<0x7884000 0x23000>;
qcom,clk-freq-out = <100000>;
qcom,clk-freq-in = <19200000>;
qcom,disable-dma;
qcom,master-id = <86>;
};
Gilad Avidov (1):
of_propery_map: compact interface for Device-Tree
Documentation/devicetree/of_property_map.txt | 76 ++++++++++++++++++++++
drivers/of/Makefile | 2 +-
drivers/of/of_property_map.c | 88 ++++++++++++++++++++++++++
include/linux/of_property_map.h | 74 ++++++++++++++++++++++
4 files changed, 239 insertions(+), 1 deletion(-)
create mode 100644 Documentation/devicetree/of_property_map.txt
create mode 100644 drivers/of/of_property_map.c
create mode 100644 include/linux/of_property_map.h
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