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SubjectRe: setting miscdevice.parent after misc_register()
On Tue, 8 Jun 2010 12:11:44 +0900
Akinobu Mita <akinobu.mita@gmail.com> wrote:

> In drivers/watchdog/at32ap700x_wdt.c, and drivers/watchdog/sch311x_wdt.c
> miscdevice.parent is set after misc_register().
>
> drivers/watchdog/at32ap700x_wdt.c:
>
> ret = misc_register(&wdt->miscdev);
> ...
> wdt->miscdev.parent = &pdev->dev;
>
> But it does nothing. (the miscdevice will not be a child of that parent
> device in sysfs)
>
> So should it be set before misc_register() or just keep it as-is?

AFAICT I think it is unsafe to have misc_register() before the last
parts of the probe function. The misc_register() should be the last
call in _probe().

Something ala the following...

From 8439126716c3cf887c6453c9543cca5b58ac9c81 Mon Sep 17 00:00:00 2001
From: Hans-Christian Egtvedt <hans-christian.egtvedt@atmel.com>
Date: Tue, 8 Jun 2010 08:44:32 +0200
Subject: [PATCH] at32ap700x_wdt: register misc device last in probe() function

This patch reworks the probe() function in the at32ap700x_wdt driver, this to
make sure the miscdev is properly initialized and the driver is ready to be
accessed.

Signed-off-by: Hans-Christian Egtvedt <hans-christian.egtvedt@atmel.com>
---
drivers/watchdog/at32ap700x_wdt.c | 16 ++++++++++------
1 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/drivers/watchdog/at32ap700x_wdt.c b/drivers/watchdog/at32ap700x_wdt.c
index 1cddf92..750bc52 100644
--- a/drivers/watchdog/at32ap700x_wdt.c
+++ b/drivers/watchdog/at32ap700x_wdt.c
@@ -346,9 +346,13 @@ static int __init at32_wdt_probe(struct platform_device *pdev)
} else {
wdt->users = 0;
}
- wdt->miscdev.minor = WATCHDOG_MINOR;
- wdt->miscdev.name = "watchdog";
- wdt->miscdev.fops = &at32_wdt_fops;
+
+ wdt->miscdev.minor = WATCHDOG_MINOR;
+ wdt->miscdev.name = "watchdog";
+ wdt->miscdev.fops = &at32_wdt_fops;
+ wdt->miscdev.parent = &pdev->dev;
+
+ platform_set_drvdata(pdev, wdt);

if (at32_wdt_settimeout(timeout)) {
at32_wdt_settimeout(TIMEOUT_DEFAULT);
@@ -360,17 +364,17 @@ static int __init at32_wdt_probe(struct platform_device *pdev)
ret = misc_register(&wdt->miscdev);
if (ret) {
dev_dbg(&pdev->dev, "failed to register wdt miscdev\n");
- goto err_iounmap;
+ goto err_register;
}

- platform_set_drvdata(pdev, wdt);
- wdt->miscdev.parent = &pdev->dev;
dev_info(&pdev->dev,
"AT32AP700X WDT at 0x%p, timeout %d sec (nowayout=%d)\n",
wdt->regs, wdt->timeout, nowayout);

return 0;

+err_register:
+ platform_set_drvdata(pdev, NULL);
err_iounmap:
iounmap(wdt->regs);
err_free:
--
1.6.3.3
--
Best regards,
Hans-Christian Egtvedt


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