Hello Carlos, On 20.12.24 07:58, Carlos Song wrote: > > >> -----Original Message----- >> From: Oleksij Rempel <o.rempel@xxxxxxxxxxxxxx> >> Sent: Friday, December 20, 2024 2:13 PM >> To: Carlos Song <carlos.song@xxxxxxx> >> Cc: Andi Shyti <andi.shyti@xxxxxxxxxx>; Frank Li <frank.li@xxxxxxx>; >> kernel@xxxxxxxxxxxxxx; shawnguo@xxxxxxxxxx; s.hauer@xxxxxxxxxxxxxx; >> festevam@xxxxxxxxx; linux-i2c@xxxxxxxxxxxxxxx; imx@xxxxxxxxxxxxxxx; >> linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Clark Wang >> <xiaoning.wang@xxxxxxx>; Ahmad Fatoum <a.fatoum@xxxxxxxxxxxxxx> >> Subject: [EXT] Re: [PATCH v5] i2c: imx: support DMA defer probing >> >> Caution: This is an external email. Please take care when clicking links or >> opening attachments. When in doubt, report the message using the 'Report this >> email' button >> >> >> On Fri, Dec 20, 2024 at 05:59:38AM +0000, Carlos Song wrote: >>>>> So we make this logic. Anyway we let the I2C controller registered >>>>> whether >>>> DMA is available or not(except defer probe). >>>>> Ignoring ENODEV and EPROBE_DEFER makes it looks like nothing >>>>> happened if >>>> DMA is defer probed or not enabled(This is an expected). >>>>> However we still need i2c DMA status is known when meet an >>>>> unexpected >>>> error, so we use dev_err_probe() to print error. >>>> >>>> Why dev_err_probe() instead of dev_err()? >>>> >>> Hi, >>> In patch V2 discussion, Marc suggested just return dev_err_probe(), >>> but I don't accept it so I choose to use dev_err_probe() to print error in V3.[1] >> In this case, the two APIs have the same function, do you mean dev_err() is more >> suitable? >> >> Yes, dev_err_probe() should be used in combination with return. For >> example: >> return dev_err_probe(...); >> >> It will pass the return value on exit of the function and optionally print of the >> error message if it is not EPROBE_DEFER. Practically it replace commonly used >> coding pattern: >> if (ret == -EPROBE_DEFER) { >> return ret; >> } else if (ret) { >> dev_err(..); >> return ret; >> } >> > Hi, > > Get your good point. I will change my code in V6: > + ret = i2c_imx_dma_request(i2c_imx, phy_addr); > + if (ret) { > + if (ret == -EPROBE_DEFER) > + goto clk_notifier_unregister; > + else if (ret == -ENODEV) > + dev_dbg(&pdev->dev, "Only use PIO mode\n"); > + else > + dev_err(&pdev->dev, "Failed to setup DMA, only use PIO mode\n"); > + } > > I think this is what you want to see, right? This loses the information why the error happens (ret). Using dev_err_probe even if no probe deferral is expected in that branch is perfectly fine and the kernel-doc even points it out: Using this helper in your probe function is totally fine even if @err is known to never be -EPROBE_DEFER. Cheers, Ahmad > >> -- >> Pengutronix e.K. | >> | >> Steuerwalder Str. 21 | >> http://www.pen/ >> gutronix.de%2F&data=05%7C02%7Ccarlos.song%40nxp.com%7C2950266755a >> 241c00a9208dd20bd5cf2%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0 >> %7C638702719862691439%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGki >> OnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ >> %3D%3D%7C0%7C%7C%7C&sdata=aIuzJP0v5C6HzOCGnCHobK9Llml3thHclTwu >> CjD13IM%3D&reserved=0 | >> 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 >> | >> Amtsgericht Hildesheim, HRA 2686 | Fax: >> +49-5121-206917-5555 | > -- Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |