linux-kernel - Re: [PATCH] tpm: Fix initialization of the cdev

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Date:	Wed, 1 Jul 2015 15:06:05 -0700
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	Jason Gunthorpe <jgunthorpe@...idianresearch.com>
Cc:	Peter Huewe <peterhuewe@....de>,
	Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
	"moderated list:TPM DEVICE DRIVER" 
	<tpmdd-devel@...ts.sourceforge.net>,
	open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] tpm: Fix initialization of the cdev

On Tue, Jun 30, 2015 at 01:15:31PM -0600, Jason Gunthorpe wrote:
> When a cdev is contained in a dynamic structure the cdev parent kobj
> should be set to the kobj that controls the lifetime of the enclosing
> structure. In TPM's case this is the embedded struct device.
> 
> Also, cdev_init 0's the whole structure, so all sets must be after,
> not before. This fixes module ref counting and cdev.
> 
> Fixes: 313d21eeab92 ("tpm: device class for tpm")
> Signed-off-by: Jason Gunthorpe <jgunthorpe@...idianresearch.com>

Right, when embedding cdev its lifetime should be tied to the lifetime
of the enclosing structure.

Reviewed-by: Dmitry Torokhov <dmitry.torokhov@...il.com>

> ---
>  drivers/char/tpm/tpm-chip.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> Peter, I've only compile tests this. Thanks
> 
> diff --git a/drivers/char/tpm/tpm-chip.c b/drivers/char/tpm/tpm-chip.c
> index 283f00a7f036..1082d4bb016a 100644
> --- a/drivers/char/tpm/tpm-chip.c
> +++ b/drivers/char/tpm/tpm-chip.c
> @@ -129,8 +129,9 @@ struct tpm_chip *tpmm_chip_alloc(struct device *dev,
>  
>  	device_initialize(&chip->dev);
>  
> -	chip->cdev.owner = chip->pdev->driver->owner;
>  	cdev_init(&chip->cdev, &tpm_fops);
> +	chip->cdev.owner = chip->pdev->driver->owner;
> +	chip->cdev.kobj.parent = &chip->dev.kobj;
>  
>  	return chip;
>  }
> -- 
> 2.1.4
> --
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-- 
Dmitry
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