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Message-ID: <alpine.DEB.2.20.1703132315120.4053@hadrien>
Date: Mon, 13 Mar 2017 23:17:41 +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 v2] staging: sm750fb: Improved code
readability
On Mon, 13 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 v2
> - removed the error.
>
> drivers/staging/sm750fb/ddk750_mode.c | 103 ++++++++++++++++------------------
> 1 file changed, 49 insertions(+), 54 deletions(-)
>
> diff --git a/drivers/staging/sm750fb/ddk750_mode.c b/drivers/staging/sm750fb/ddk750_mode.c
> index 25da678179f7..6dd52b450367 100644
> --- a/drivers/staging/sm750fb/ddk750_mode.c
> +++ b/drivers/staging/sm750fb/ddk750_mode.c
> @@ -77,37 +77,34 @@ static int programModeRegisters(struct _mode_parameter_t *pModeParam, struct pll
> int ret = 0;
> int cnt = 0;
> unsigned int tmp, reg;
> + unsigned int cht = CRT_HORIZONTAL_TOTAL;
> + unsigned int cvt = CRT_VERTICAL_TOTAL;
> + unsigned int chs = CRT_HORIZONTAL_SYNC;
> + unsigned int cvs = CRT_VERTICAL_SYNC;
> + unsigned int chssm = CRT_HORIZONTAL_SYNC_START_MASK;
> + unsigned int cvssm = CRT_VERTICAL_SYNC_START_MASK;
> + unsigned int chtdem = CRT_HORIZONTAL_TOTAL_DISPLAY_END_MASK;
> + unsigned int cvtdem = CRT_VERTICAL_TOTAL_DISPLAY_END_MASK;
> + unsigned int chttm = CRT_HORIZONTAL_TOTAL_TOTAL_MASK;
> + unsigned int cvttm = CRT_VERTICAL_TOTAL_TOTAL_MASK;
> + unsigned int chswm = CRT_HORIZONTAL_SYNC_WIDTH_MASK;
> + unsigned int cvshm = CRT_VERTICAL_SYNC_HEIGHT_MASK;
> + unsigned int phde = pModeParam->horizontal_display_end - 1;
> + unsigned int pvde = pModeParam->vertical_display_end - 1;
> + unsigned int phss = pModeParam->horizontal_sync_start - 1;
> + unsigned int pvss = pModeParam->vertical_sync_start - 1;
I dont think this is a good solution. The new names are not very
memorable, and they are not used near their definition. You could instead
name a subexpression, and put the initialization right next to where the
variable would be used. So for a trivial example, you could turn
x = (a + b) * c;
into
tmp = a * b;
x = tmp * c;
What you have in the definition of tmp should do some computation but
be able to be laid out in a readable manner.
julia
>
> 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));
> +
> + poke32(cht, (((pModeParam->horizontal_total - 1) << CRT_HORIZONTAL_TOTAL_TOTAL_SHIFT) & chttm) | (phde & chtdem));
> +
> + poke32(chs, ((pModeParam->horizontal_sync_width << CRT_HORIZONTAL_SYNC_WIDTH_SHIFT) & chswm) | (phss & chssm));
> +
> + poke32(cvt, (((pModeParam->vertical_total - 1) << CRT_VERTICAL_TOTAL_TOTAL_SHIFT) & cvttm) | (pvde & cvtdem));
> +
> + poke32(cvs, ((pModeParam->vertical_sync_height << CRT_VERTICAL_SYNC_HEIGHT_SHIFT) & cvshm) | (pvss & cvssm));
>
> tmp = DISPLAY_CTRL_TIMING | DISPLAY_CTRL_PLANE;
> if (pModeParam->vertical_sync_polarity)
> @@ -128,36 +125,34 @@ static int programModeRegisters(struct _mode_parameter_t *pModeParam, struct pll
>
> } else if (pll->clockType == PRIMARY_PLL) {
> unsigned int reserved;
> + unsigned int pht = PANEL_HORIZONTAL_TOTAL;
> + unsigned int pvt = PANEL_VERTICAL_TOTAL;
> + unsigned int phs = PANEL_HORIZONTAL_SYNC;
> + unsigned int pvs = PANEL_VERTICAL_SYNC;
> + unsigned int phssm = PANEL_HORIZONTAL_SYNC_START_MASK;
> + unsigned int pvssm = PANEL_VERTICAL_SYNC_START_MASK;
> + unsigned int phtdem = PANEL_HORIZONTAL_TOTAL_DISPLAY_END_MASK;
> + unsigned int pvtdem = PANEL_VERTICAL_TOTAL_DISPLAY_END_MASK;
> + unsigned int phttm = PANEL_HORIZONTAL_TOTAL_TOTAL_MASK;
> + unsigned int pvttm = PANEL_VERTICAL_TOTAL_TOTAL_MASK;
> + unsigned int phswm = PANEL_HORIZONTAL_SYNC_WIDTH_MASK;
> + unsigned int pvshm = PANEL_VERTICAL_SYNC_HEIGHT_MASK;
> + unsigned int phde = pModeParam->horizontal_display_end - 1;
> + unsigned int pvde = pModeParam->vertical_display_end - 1;
> + unsigned int phss = pModeParam->horizontal_sync_start - 1;
> + unsigned int pvss = pModeParam->vertical_sync_start - 1;
>
> poke32(PANEL_PLL_CTRL, sm750_format_pll_reg(pll));
>
> - reg = ((pModeParam->horizontal_total - 1) <<
> - PANEL_HORIZONTAL_TOTAL_TOTAL_SHIFT) &
> - PANEL_HORIZONTAL_TOTAL_TOTAL_MASK;
> - reg |= ((pModeParam->horizontal_display_end - 1) &
> - PANEL_HORIZONTAL_TOTAL_DISPLAY_END_MASK);
> - poke32(PANEL_HORIZONTAL_TOTAL, reg);
> -
> - poke32(PANEL_HORIZONTAL_SYNC,
> - ((pModeParam->horizontal_sync_width <<
> - PANEL_HORIZONTAL_SYNC_WIDTH_SHIFT) &
> - PANEL_HORIZONTAL_SYNC_WIDTH_MASK) |
> - ((pModeParam->horizontal_sync_start - 1) &
> - PANEL_HORIZONTAL_SYNC_START_MASK));
> -
> - poke32(PANEL_VERTICAL_TOTAL,
> - (((pModeParam->vertical_total - 1) <<
> - PANEL_VERTICAL_TOTAL_TOTAL_SHIFT) &
> - PANEL_VERTICAL_TOTAL_TOTAL_MASK) |
> - ((pModeParam->vertical_display_end - 1) &
> - PANEL_VERTICAL_TOTAL_DISPLAY_END_MASK));
> -
> - poke32(PANEL_VERTICAL_SYNC,
> - ((pModeParam->vertical_sync_height <<
> - PANEL_VERTICAL_SYNC_HEIGHT_SHIFT) &
> - PANEL_VERTICAL_SYNC_HEIGHT_MASK) |
> - ((pModeParam->vertical_sync_start - 1) &
> - PANEL_VERTICAL_SYNC_START_MASK));
> + reg = ((pModeParam->horizontal_total - 1) << PANEL_HORIZONTAL_TOTAL_TOTAL_SHIFT) & phttm;
> + reg |= (phde & phtdem);
> + poke32(pht, reg);
> +
> + poke32(phs, ((pModeParam->horizontal_sync_width << PANEL_HORIZONTAL_SYNC_WIDTH_SHIFT) & phswm) | (phss & phssm));
> +
> + poke32(pvt, (((pModeParam->vertical_total - 1) << PANEL_VERTICAL_TOTAL_TOTAL_SHIFT) & pvttm) | (pvde & pvtdem));
> +
> + poke32(pvs, ((pModeParam->vertical_sync_height << PANEL_VERTICAL_SYNC_HEIGHT_SHIFT) & pvshm) | (pvss & pvssm));
>
> tmp = DISPLAY_CTRL_TIMING | DISPLAY_CTRL_PLANE;
> if (pModeParam->vertical_sync_polarity)
> --
> 2.11.0
>
> --
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