Hi, The only way to probe an OF driver is when a match is found in the device table. And hence checking for of_match_device() is redundant and instead it is better to use of_device_get_match_data() to get the matched driver specific data in the probe function. For instance: https://lkml.org/lkml/2018/4/30/66 static int mmio_74xx_gpio_probe(struct platform_device *pdev) { - const struct of_device_id *of_id; struct mmio_74xx_gpio_priv *priv; struct resource *res; void __iomem *dat; int err; - of_id = of_match_device(mmio_74xx_gpio_ids, &pdev->dev); - if (!of_id) - return -ENODEV; - priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL); if (!priv) return -ENOMEM; + priv->flags = (uintptr_t)of_device_get_match_data(&pdev->dev); + res = platform_get_resource(pdev, IORESOURCE_MEM, 0); dat = devm_ioremap_resource(&pdev->dev, res); if (IS_ERR(dat)) return PTR_ERR(dat); - priv->flags = (uintptr_t) of_id->data; - -------------------------------------------------------------------------- In the above example of_match_device() is useless since the probe occurs *only* when a match is found and therefore checking again is redundant. But now my question is if this is the case, then when does of_match_device() return NULL ? When is the error handling required ? There are places where it is done as "safe-play" coding as suggested to me by Jonathan Cameron previosuly https://lkml.org/lkml/2018/3/16/1245 I am working on a Coccinelle SmPL rule with the help of Julia Lawall to replace of_match_device() + error handling with of_device_get_match_data() simply. I am testing the refactoring changes and it is at: https://github.com/himanshujha199640/linux-next/commit/efb7ed923bd00c86fe0a4e67e2ddb636ff0e0ff4 ------------------------------------------------------------------------------- Some statistics found by Julia Lawall: f_match_device with check: 257/283 no of tbl: 39, of tbl only: 148, other tbl only: 4, multi tbl: 66 has of_match_ptr: 87, no of_match_ptr: 170 of_match_device without check: 26/283 no of tbl: 14, of tbl only: 11, other tbl only: 0, multi tbl: 1 has of_match_ptr: 6, no of_match_ptr: 20 of_device_get_match_data with check: 158/212 no of tbl: 29, of tbl only: 78, other tbl only: 0, multi tbl: 51 has of_match_ptr: 53, no of_match_ptr: 105 of_device_get_match_data without check: 54/212 no of tbl: 13, of tbl only: 40, other tbl only: 0, multi tbl: 1 has of_match_ptr: 8, no of_match_ptr: 46 Multi table files without an of_match_device check drivers/mmc/host/mxs-mmc.c Multi table files without an of_device_get_match_data check drivers/clk/clk-versaclock5.c of_match_ptr files without an of_match_device check drivers/pinctrl/mvebu/pinctrl-orion.c drivers/tty/serial/mvebu-uart.c drivers/misc/eeprom/eeprom_93xx46.c arch/arm/plat-pxa/ssp.c drivers/soc/mediatek/mtk-scpsys.c drivers/pinctrl/mvebu/pinctrl-armada-cp110.c of_match_ptr files without an of_device_get_match_data check drivers/gpu/drm/nouveau/nouveau_platform.c drivers/gpio/gpio-pxa.c drivers/gpio/gpio-rcar.c drivers/iommu/arm-smmu.c drivers/usb/gadget/udc/renesas_usb3.c drivers/i2c/busses/i2c-mt65xx.c drivers/iommu/ipmmu-vmsa.c drivers/mtd/nand/raw/mtk_ecc.c other table only (no of_device_id matching) drivers/mfd/wm831x-i2c.c drivers/macintosh/macio_asic.c drivers/mfd/max14577.c drivers/mfd/wm831x-spi.c -------------------------------------------------------------------------- -- Himanshu Jha Undergraduate Student Department of Electronics & Communication Guru Tegh Bahadur Institute of Technology -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
