linux-kernel - Re: [PATCH V4 09/12] boot_constraint: Add earlycon helper

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Message-ID: <20171213094450.GD13194@kroah.com>
Date:   Wed, 13 Dec 2017 10:44:50 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     Vincent Guittot <vincent.guittot@...aro.org>,
        Stephen Boyd <sboyd@...eaurora.org>,
        Rajendra Nayak <rnayak@...eaurora.org>,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        robdclark@...il.com, s.hauer@...gutronix.de,
        l.stach@...gutronix.de, shawnguo@...nel.org, fabio.estevam@....com,
        nm@...com, xuwei5@...ilicon.com, robh+dt@...nel.org
Subject: Re: [PATCH V4 09/12] boot_constraint: Add earlycon helper

On Sun, Oct 29, 2017 at 07:18:57PM +0530, Viresh Kumar wrote:
> Getting boot messages during initial kernel boot is a common problem,
> which (almost) everyone wants to solve. Considering that this would be
> required by multiple platforms, provide a helper to check if "earlycon"
> or "earlyprintk" boot arguments are passed to kernel or not. The
> platforms can use this helper to add serial constraints only if earlycon
> if required.
> 
> Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
> ---
>  drivers/boot_constraints/Makefile |  2 +-
>  drivers/boot_constraints/serial.c | 28 ++++++++++++++++++++++++++++
>  include/linux/boot_constraint.h   |  2 ++
>  3 files changed, 31 insertions(+), 1 deletion(-)
>  create mode 100644 drivers/boot_constraints/serial.c
> 
> diff --git a/drivers/boot_constraints/Makefile b/drivers/boot_constraints/Makefile
> index a765094623a3..0d4f88bb767c 100644
> --- a/drivers/boot_constraints/Makefile
> +++ b/drivers/boot_constraints/Makefile
> @@ -1,3 +1,3 @@
>  # Makefile for device boot constraints
>  
> -obj-y := clk.o deferrable_dev.o core.o pm.o supply.o
> +obj-y := clk.o deferrable_dev.o core.o pm.o serial.o supply.o
> diff --git a/drivers/boot_constraints/serial.c b/drivers/boot_constraints/serial.c
> new file mode 100644
> index 000000000000..d0d07d4aa6af
> --- /dev/null
> +++ b/drivers/boot_constraints/serial.c
> @@ -0,0 +1,28 @@
> +/*
> + * This contains helpers related to serial boot constraints.
> + *
> + * Copyright (C) 2017 Linaro.
> + * Viresh Kumar <viresh.kumar@...aro.org>
> + *
> + * This file is released under the GPLv2.
> + */
> +
> +#include <linux/init.h>
> +
> +static bool earlycon_boot_constraints_enabled __initdata;
> +
> +bool __init boot_constraint_earlycon_enabled(void)
> +{
> +	return earlycon_boot_constraints_enabled;
> +}
> +
> +static int __init enable_earlycon_boot_constraints(char *str)
> +{
> +	earlycon_boot_constraints_enabled = true;
> +
> +	return 0;
> +}
> +__setup_param("earlycon", boot_constraint_earlycon,
> +	      enable_earlycon_boot_constraints, 0);
> +__setup_param("earlyprintk", boot_constraint_earlyprintk,
> +	      enable_earlycon_boot_constraints, 0);
> diff --git a/include/linux/boot_constraint.h b/include/linux/boot_constraint.h
> index c110b36e490f..aeada69b87e6 100644
> --- a/include/linux/boot_constraint.h
> +++ b/include/linux/boot_constraint.h
> @@ -10,6 +10,7 @@
>  #define _LINUX_BOOT_CONSTRAINT_H
>  
>  #include <linux/err.h>
> +#include <linux/init.h>
>  #include <linux/types.h>
>  
>  struct device;
> @@ -58,6 +59,7 @@ int dev_boot_constraint_add(struct device *dev,
>  void dev_boot_constraints_remove(struct device *dev);
>  void dev_boot_constraint_add_deferrable_of(struct dev_boot_constraint_of *oconst,
>  					   int count);
> +bool __init boot_constraint_earlycon_enabled(void);
>  #else
>  static inline
>  int dev_boot_constraint_add(struct device *dev,

No need for this function if it's not enabled?

And this feels really odd, does it really save any work for the
individual "constraint" to check for this option?  I'm all for helper
functions, but this feels like more work than it's worth...

thanks,

greg k-h