linux-kernel - Re: [PATCH 08/11] tty: vt: simplify some unicode conditions

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Message-ID: <2a1c8867-92e9-edce-257e-89a343efe836@linux.intel.com>
Date:   Thu, 12 Jan 2023 11:52:14 +0200 (EET)
From:   Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To:     "Jiri Slaby (SUSE)" <jirislaby@...nel.org>
cc:     gregkh@...uxfoundation.org, Kees Cook <keescook@...omium.org>,
        linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 08/11] tty: vt: simplify some unicode conditions

On Thu, 12 Jan 2023, Jiri Slaby (SUSE) wrote:

> After previous patches, we can simply test vc->vc_uni_lines, so do so in
> many unicode functions. This makes the code more compact. And even use
>   if (!)
>     return;
> in vc_uniscr_scroll(), so that the whole code is indented on the left.
> 
> Signed-off-by: Jiri Slaby (SUSE) <jirislaby@...nel.org>
> ---
>  drivers/tty/vt/vt.c | 85 +++++++++++++++++++--------------------------
>  1 file changed, 36 insertions(+), 49 deletions(-)
> 
> diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
> index db72375141b0..74db07b32abe 100644
> --- a/drivers/tty/vt/vt.c
> +++ b/drivers/tty/vt/vt.c
> @@ -357,18 +357,14 @@ static void vc_uniscr_set(struct vc_data *vc, u32 **new_uni_lines)
>  
>  static void vc_uniscr_putc(struct vc_data *vc, u32 uc)
>  {
> -	u32 **uni_lines = vc->vc_uni_lines;
> -
> -	if (uni_lines)
> -		uni_lines[vc->state.y][vc->state.x] = uc;
> +	if (vc->vc_uni_lines)
> +		vc->vc_uni_lines[vc->state.y][vc->state.x] = uc;
>  }
>  
>  static void vc_uniscr_insert(struct vc_data *vc, unsigned int nr)
>  {
> -	u32 **uni_lines = vc->vc_uni_lines;
> -
> -	if (uni_lines) {
> -		u32 *ln = uni_lines[vc->state.y];
> +	if (vc->vc_uni_lines) {
> +		u32 *ln = vc->vc_uni_lines[vc->state.y];
>  		unsigned int x = vc->state.x, cols = vc->vc_cols;
>  
>  		memmove(&ln[x + nr], &ln[x], (cols - x - nr) * sizeof(*ln));
> @@ -378,10 +374,8 @@ static void vc_uniscr_insert(struct vc_data *vc, unsigned int nr)
>  
>  static void vc_uniscr_delete(struct vc_data *vc, unsigned int nr)
>  {
> -	u32 **uni_lines = vc->vc_uni_lines;
> -
> -	if (uni_lines) {
> -		u32 *ln = uni_lines[vc->state.y];
> +	if (vc->vc_uni_lines) {
> +		u32 *ln = vc->vc_uni_lines[vc->state.y];
>  		unsigned int x = vc->state.x, cols = vc->vc_cols;
>  
>  		memcpy(&ln[x], &ln[x + nr], (cols - x - nr) * sizeof(*ln));
> @@ -392,59 +386,52 @@ static void vc_uniscr_delete(struct vc_data *vc, unsigned int nr)
>  static void vc_uniscr_clear_line(struct vc_data *vc, unsigned int x,
>  				 unsigned int nr)
>  {
> -	u32 **uni_lines = vc->vc_uni_lines;
> -
> -	if (uni_lines) {
> -		u32 *ln = uni_lines[vc->state.y];
> -
> -		memset32(&ln[x], ' ', nr);
> -	}
> +	if (vc->vc_uni_lines)
> +		memset32(&vc->vc_uni_lines[vc->state.y][x], ' ', nr);
>  }
>  
>  static void vc_uniscr_clear_lines(struct vc_data *vc, unsigned int y,
>  				  unsigned int nr)
>  {
> -	u32 **uni_lines = vc->vc_uni_lines;
> -
> -	if (uni_lines) {
> -		unsigned int cols = vc->vc_cols;
> -
> +	if (vc->vc_uni_lines)
>  		while (nr--)
> -			memset32(uni_lines[y++], ' ', cols);
> -	}
> +			memset32(vc->vc_uni_lines[y++], ' ', vc->vc_cols);
>  }
>  
>  static void vc_uniscr_scroll(struct vc_data *vc, unsigned int t, unsigned int b,
>  			     enum con_scroll dir, unsigned int nr)
>  {
>  	u32 **uni_lines = vc->vc_uni_lines;
> +	unsigned int i, j, k, sz, d, clear;
>  
> -	if (uni_lines) {
> -		unsigned int i, j, k, sz, d, clear;
> +	if (!uni_lines)
> +		return;
>  
> -		sz = b - t;
> -		clear = b - nr;
> -		d = nr;
> -		if (dir == SM_DOWN) {
> -			clear = t;
> -			d = sz - nr;
> -		}
> -		for (i = 0; i < gcd(d, sz); i++) {
> -			u32 *tmp = uni_lines[t + i];
> -			j = i;
> -			while (1) {
> -				k = j + d;
> -				if (k >= sz)
> -					k -= sz;
> -				if (k == i)
> -					break;
> -				uni_lines[t + j] = uni_lines[t + k];
> -				j = k;
> -			}
> -			uni_lines[t + j] = tmp;
> +	sz = b - t;
> +	clear = b - nr;
> +	d = nr;
> +
> +	if (dir == SM_DOWN) {
> +		clear = t;
> +		d = sz - nr;
> +	}
> +
> +	for (i = 0; i < gcd(d, sz); i++) {
> +		u32 *tmp = uni_lines[t + i];
> +		j = i;
> +		while (1) {
> +			k = j + d;
> +			if (k >= sz)
> +				k -= sz;
> +			if (k == i)
> +				break;
> +			uni_lines[t + j] = uni_lines[t + k];
> +			j = k;
>  		}
> -		vc_uniscr_clear_lines(vc, clear, nr);
> +		uni_lines[t + j] = tmp;
>  	}
> +
> +	vc_uniscr_clear_lines(vc, clear, nr);
>  }
>  
>  static void vc_uniscr_copy_area(u32 **dst_lines,
> 

Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>

With the note that increased density of "vc[-_]" per line feels a step 
backwards on readability even if the number of lines is less, IMHO.

-- 
 i.