CODEWITHSUNDEEP
clinux-kernellinux-device-driverarm64
Milan
Milan

Reputation: 1529

Understanding about Linux regmap's devm_regmap_init_mmio

I would like to know, how devm_regmap_init_mmio() can be used to export a regmap for 16 bytes (span over two subregions). For instance, from one of the driver in Linux:

    regs = devm_platform_ioremap_resource_byname(pdev, "ehb");
    if (IS_ERR(regs)) {
        dev_err(apb->dev, "Couldn't map APB EHB registers\n");
        return PTR_ERR(regs);
    }

    apb->regs = devm_regmap_init_mmio(apb->dev, regs, &bt1_apb_regmap_cfg);
    if (IS_ERR(apb->regs)) {
        dev_err(apb->dev, "Couldn't create APB EHB regmap\n");
        return PTR_ERR(apb->regs);

' with bt1_apb_regmap_cfg filled as

     static const struct regmap_config bt1_apb_regmap_cfg = {
    .reg_bits = 32,
    .val_bits = 32,
    .reg_stride = 4,
    .max_register = APB_EHB_TIMEOUT,
    .fast_io = true
};

here looks like whole register range is exported using devm_regmap_init_mmio but is there a way to export only 16 byters span across four register ?

Also, what are these fields .max_register and .reg_stride means here ?

Upvotes: 0

Views: 768

Answers (1)

Varun
Varun

Reputation: 477

max_register means if the register range is from 0x1000 to 0x1040 than than max_register = 0x40

reg_stride means the register address should be multiple of this value

Upvotes: 1

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