linux-kernel - Re: [Outreachy kernel] [PATCH v3] staging: sm750fb: Code readability is improved

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Message-ID: <alpine.DEB.2.20.1703191409140.2108@hadrien>
Date:   Sun, 19 Mar 2017 14:11:01 +0100 (CET)
From:   Julia Lawall <julia.lawall@...6.fr>
To:     Arushi Singhal <arushisinghal19971997@...il.com>
cc:     sudipm.mukherjee@...il.com,
        Teddy Wang <teddy.wang@...iconmotion.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-fbdev@...r.kernel.org, devel@...verdev.osuosl.org,
        linux-kernel@...r.kernel.org, outreachy-kernel@...glegroups.com
Subject: Re: [Outreachy kernel] [PATCH v3] staging: sm750fb: Code readability
 is improved



On Sun, 19 Mar 2017, Arushi Singhal wrote:

> New variables are added to make the code more readable.
>
> Signed-off-by: Arushi Singhal <arushisinghal19971997@...il.com>
> ---
>  changes in v3
>  -try to make the code much more readable.
>
>  drivers/staging/sm750fb/ddk750_mode.c | 61 ++++++++++++++++++++---------------
>  1 file changed, 35 insertions(+), 26 deletions(-)
>
> diff --git a/drivers/staging/sm750fb/ddk750_mode.c b/drivers/staging/sm750fb/ddk750_mode.c
> index eea5aef2956f..5f18ce4d10de 100644
> --- a/drivers/staging/sm750fb/ddk750_mode.c
> +++ b/drivers/staging/sm750fb/ddk750_mode.c
> @@ -81,33 +81,42 @@ static int programModeRegisters(mode_parameter_t *pModeParam, struct pll_value *
>  	if (pll->clockType == SECONDARY_PLL) {
>  		/* programe secondary pixel clock */
>  		poke32(CRT_PLL_CTRL, sm750_format_pll_reg(pll));
> -		poke32(CRT_HORIZONTAL_TOTAL,
> -		       (((pModeParam->horizontal_total - 1) <<
> -			 CRT_HORIZONTAL_TOTAL_TOTAL_SHIFT) &
> -			CRT_HORIZONTAL_TOTAL_TOTAL_MASK) |
> -		       ((pModeParam->horizontal_display_end - 1) &
> -			CRT_HORIZONTAL_TOTAL_DISPLAY_END_MASK));
> -
> -		poke32(CRT_HORIZONTAL_SYNC,
> -		       ((pModeParam->horizontal_sync_width <<
> -			 CRT_HORIZONTAL_SYNC_WIDTH_SHIFT) &
> -			CRT_HORIZONTAL_SYNC_WIDTH_MASK) |
> -		       ((pModeParam->horizontal_sync_start - 1) &
> -			CRT_HORIZONTAL_SYNC_START_MASK));
>
> -		poke32(CRT_VERTICAL_TOTAL,
> -		       (((pModeParam->vertical_total - 1) <<
> -			 CRT_VERTICAL_TOTAL_TOTAL_SHIFT) &
> -			CRT_VERTICAL_TOTAL_TOTAL_MASK) |
> -		       ((pModeParam->vertical_display_end - 1) &
> -			CRT_VERTICAL_TOTAL_DISPLAY_END_MASK));
> -
> -		poke32(CRT_VERTICAL_SYNC,
> -		       ((pModeParam->vertical_sync_height <<
> -			 CRT_VERTICAL_SYNC_HEIGHT_SHIFT) &
> -			CRT_VERTICAL_SYNC_HEIGHT_MASK) |
> -		       ((pModeParam->vertical_sync_start - 1) &
> -			CRT_VERTICAL_SYNC_START_MASK));
> +		unsigned int a = (pModeParam->horizontal_total - 1) <<
> +				CRT_HORIZONTAL_TOTAL_TOTAL_SHIFT;
> +		unsigned int b = a & CRT_HORIZONTAL_TOTAL_TOTAL_MASK;
> +		unsigned int c = (pModeParam->horizontal_display_end - 1) &
> +				CRT_HORIZONTAL_TOTAL_DISPLAY_END_MASK;
> +		unsigned int temp = b | c;
> +
> +		poke32(CRT_HORIZONTAL_TOTAL, temp);
> +
> +		unsigned int a = (pModeParam->horizontal_sync_width <<
> +				CRT_HORIZONTAL_SYNC_WIDTH_SHIFT);
> +		unsigned int b = a & CRT_HORIZONTAL_SYNC_WIDTH_MASK;
> +		unsigned int c = (pModeParam->horizontal_sync_start - 1) &
> +				CRT_HORIZONTAL_SYNC_START_MASK;
> +		unsigned int temp = b | c;

This is back to the original incorrect solution.  You can't declare
variables on the fly in Linux code.  Variables have to be declared at the
top of a block.

But you can reuse the same variables over and over, if no one cares about
their previous values.

julia


> +
> +		poke32(CRT_HORIZONTAL_SYNC, temp);
> +
> +		unsigned int a = (pModeParam->vertical_total - 1) <<
> +				CRT_VERTICAL_TOTAL_TOTAL_SHIFT;
> +		unsigned int b = a & CRT_VERTICAL_TOTAL_TOTAL_MASK;
> +		unsigned int c = (pModeParam->vertical_display_end - 1) &
> +				CRT_VERTICAL_TOTAL_DISPLAY_END_MASK;
> +		unsigned int temp = b | c;
> +
> +		poke32(CRT_VERTICAL_TOTAL, temp);
> +
> +		unsigned int a = pModeParam->vertical_sync_height <<
> +				CRT_VERTICAL_SYNC_HEIGHT_SHIFT;
> +		unsigned int b = a & CRT_VERTICAL_SYNC_HEIGHT_MASK;
> +		unsigned int c = (pModeParam->vertical_sync_start - 1) &
> +				CRT_VERTICAL_SYNC_START_MASK;
> +		unsigned int temp = b | c;
> +
> +		poke32(CRT_VERTICAL_SYNC, temp);
>
>  		tmp = DISPLAY_CTRL_TIMING | DISPLAY_CTRL_PLANE;
>  		if (pModeParam->vertical_sync_polarity)
> --
> 2.11.0
>
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