linux-kernel - Re: [PATCH] clk: Fix debugfs_create

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Message-ID: <20180102192320.GJ7997@codeaurora.org>
Date:   Tue, 2 Jan 2018 11:23:20 -0800
From:   Stephen Boyd <sboyd@...eaurora.org>
To:     Geert Uytterhoeven <geert+renesas@...der.be>
Cc:     Michael Turquette <mturquette@...libre.com>,
        linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] clk: Fix debugfs_create_*() usage

On 01/02, Geert Uytterhoeven wrote:
> When exposing data access through debugfs, the correct
> debugfs_create_*() functions must be used, depending on data type.
> 
> Remove all casts from data pointers passed to debugfs_create_*()
> functions, as such casts prevent the compiler from flagging bugs.
> 
> clk_core.rate, .accuracy, and .flags are "unsigned long", hence casting
> to "u32 *" exposed the wrong halves on big-endian 64-bit systems.
> 
> Fix .rate and .accuracy, by using debugfs_create_ulong() instead.
> 
> Fix .flags by changing the field to "unsigned int", as a change to
> debugfs_create_x64() on 64-bit systems would change the user-visible
> formatting in debugfs.
> Note that __clk_get_flags() and clk_hw_get_flags() are left unchanged
> and still return "unsigned long", to avoid having to change all their
> users.  Likewise, of_clk_detect_critical() still takes "unsigned long",
> but the comment is updated as it is never passed a real pointer to
> clk_core.flags.
> 
> Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>
> ---
> Looks like none of the 64-bit architectures support common clock yet?

arm64 does.

> ---
>  drivers/clk/clk.c | 24 ++++++++++++------------
>  1 file changed, 12 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
> index 5ec580914089510a..b23e0249f0e3c634 100644
> --- a/drivers/clk/clk.c
> +++ b/drivers/clk/clk.c
> @@ -58,7 +58,7 @@ struct clk_core {
>  	unsigned long		new_rate;
>  	struct clk_core		*new_parent;
>  	struct clk_core		*new_child;
> -	unsigned long		flags;
> +	unsigned int		flags;

This doesn't look good.

>  	bool			orphan;
>  	unsigned int		enable_count;
>  	unsigned int		prepare_count;
> @@ -2600,43 +2600,43 @@ static int clk_debug_create_one(struct clk_core *core, struct dentry *pdentry)
>  
>  	core->dentry = d;
>  
> -	d = debugfs_create_u32("clk_rate", S_IRUGO, core->dentry,
> -			(u32 *)&core->rate);
> +	d = debugfs_create_ulong("clk_rate", S_IRUGO, core->dentry,
> +				 &core->rate);

As you're changing these lines, can you also change S_IRUGO to
the octal values. That's the preferred style now.

>  	if (!d)
>  		goto err_out;
>  
> -	d = debugfs_create_u32("clk_accuracy", S_IRUGO, core->dentry,
> -			(u32 *)&core->accuracy);
> +	d = debugfs_create_ulong("clk_accuracy", S_IRUGO, core->dentry,
> +				 &core->accuracy);
>  	if (!d)
>  		goto err_out;
>  
>  	d = debugfs_create_u32("clk_phase", S_IRUGO, core->dentry,
> -			(u32 *)&core->phase);
> +			       &core->phase);
>  	if (!d)
>  		goto err_out;
>  
>  	d = debugfs_create_x32("clk_flags", S_IRUGO, core->dentry,
> -			(u32 *)&core->flags);
> +			       &core->flags);

Maybe we need a new debugfs API like debugfs_create_ulong_hex()
or something that prints out an unsigned long as a hex value?
Probably we should change it to pretty print the values and what
they correspond to, with words, because that's the least
confusing thing to do with regards to endianness. So the
clk_flags file would have something like

	CLK_SET_RATE_PARENT
	CLK_SET_RATE_GATE

if those flags are set.

We don't care about ABI here either. This is debugfs.

> @@ -3927,7 +3927,7 @@ static int parent_ready(struct device_node *np)
>   * of_clk_detect_critical() - set CLK_IS_CRITICAL flag from Device Tree
>   * @np: Device node pointer associated with clock provider
>   * @index: clock index
> - * @flags: pointer to clk_core->flags
> + * @flags: pointer to core clock flags

Please split this off into another patch.

-- 
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