From 119e9db233ad0f4cbd4cfb9f9385a7bca378b37d Mon Sep 17 00:00:00 2001 From: Zeng Chi Date: Mon, 21 Sep 2026 18:24:42 +0800 Subject: KVM: Don't pre-reserve xarray entries when storing empty/NULL attributes Skip the xarray reservation loop when clearing all memory attributes, as storing NULL only erases the entry and never needs to allocate, so no reservation (and no cleanup of a failed one) is required in that case. Suggested-by: Sean Christopherson Cc: David Ballesteros Signed-off-by: Zeng Chi Link: https://patch.msgid.link/20260921102442.1232375-1-zeng_chi911@163.com [sean: split to separate patch] Signed-off-by: Sean Christopherson --- drivers/video/fbdev/bt455.h | 90 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 90 insertions(+) create mode 100644 drivers/video/fbdev/bt455.h (limited to 'drivers/video/fbdev/bt455.h') diff --git a/drivers/video/fbdev/bt455.h b/drivers/video/fbdev/bt455.h new file mode 100644 index 000000000..dd1404b40 --- /dev/null +++ b/drivers/video/fbdev/bt455.h @@ -0,0 +1,90 @@ +/* + * linux/drivers/video/bt455.h + * + * Copyright 2003 Thiemo Seufer + * Copyright 2016 Maciej W. Rozycki + * + * This file is subject to the terms and conditions of the GNU General + * Public License. See the file COPYING in the main directory of this + * archive for more details. + */ +#include + +/* + * Bt455 byte-wide registers, 32-bit aligned. + */ +struct bt455_regs { + volatile u8 addr_cmap; + u8 pad0[3]; + volatile u8 addr_cmap_data; + u8 pad1[3]; + volatile u8 addr_clr; + u8 pad2[3]; + volatile u8 addr_ovly; + u8 pad3[3]; +}; + +static inline void bt455_select_reg(struct bt455_regs *regs, int ir) +{ + mb(); + regs->addr_cmap = ir & 0x0f; +} + +static inline void bt455_reset_reg(struct bt455_regs *regs) +{ + mb(); + regs->addr_clr = 0; +} + +/* + * Read/write to a Bt455 color map register. + */ +static inline void bt455_read_cmap_next(struct bt455_regs *regs, u8 *grey) +{ + mb(); + regs->addr_cmap_data; + rmb(); + *grey = regs->addr_cmap_data & 0xf; + rmb(); + regs->addr_cmap_data; +} + +static inline void bt455_write_cmap_next(struct bt455_regs *regs, u8 grey) +{ + wmb(); + regs->addr_cmap_data = 0x0; + wmb(); + regs->addr_cmap_data = grey & 0xf; + wmb(); + regs->addr_cmap_data = 0x0; +} + +static inline void bt455_write_ovly_next(struct bt455_regs *regs, u8 grey) +{ + wmb(); + regs->addr_ovly = 0x0; + wmb(); + regs->addr_ovly = grey & 0xf; + wmb(); + regs->addr_ovly = 0x0; +} + +static inline void bt455_read_cmap_entry(struct bt455_regs *regs, + int cr, u8 *grey) +{ + bt455_select_reg(regs, cr); + bt455_read_cmap_next(regs, grey); +} + +static inline void bt455_write_cmap_entry(struct bt455_regs *regs, + int cr, u8 grey) +{ + bt455_select_reg(regs, cr); + bt455_write_cmap_next(regs, grey); +} + +static inline void bt455_write_ovly_entry(struct bt455_regs *regs, u8 grey) +{ + bt455_reset_reg(regs); + bt455_write_ovly_next(regs, grey); +} -- cgit v1.3.1