gpio: i8255: Introduce the Intel 8255 interface library module

Exposes consumer library functions providing support for interfaces
compatible with the venerable Intel 8255 Programmable Peripheral
Interface (PPI).

The Intel 8255 PPI first appeared in the early 1970s, initially for the
Intel 8080 and later appearing in the original IBM-PC. The popularity of
the original Intel 8255 chip led to many subsequent variants and clones
of the interface in various chips and integrated circuits. Although
still popular, interfaces compatible with the Intel 8255 PPI are
nowdays typically found embedded in larger VLSI processing chips and
FPGA components rather than as discrete ICs.

A CONFIG_GPIO_I8255 Kconfig option is introduced by this patch. Modules
wanting access to these i8255 library functions should select this
Kconfig option, and import the I8255 symbol namespace.

Tested-by: Fred Eckert <Frede@cmslaser.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Cc: John Hentges <jhentges@accesio.com>
Cc: Jay Dolan <jay.dolan@accesio.com>
Cc: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: William Breathitt Gray <william.gray@linaro.org>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>

1 files changed, 46 insertions, 0 deletions

diff --git a/drivers/gpio/gpio-i8255.h b/drivers/gpio/gpio-i8255.h
new file mode 100644
index 000000000000..d9084aae9446
--- /dev/null
+++ b/drivers/gpio/gpio-i8255.h
@@ -0,0 +1,46 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Copyright 2022 William Breathitt Gray */
+#ifndef _I8255_H_
+#define _I8255_H_
+
+#include <linux/spinlock.h>
+#include <linux/types.h>
+
+/**
+ * struct i8255 - Intel 8255 register structure
+ * @port:	Port A, B, and C
+ * @control:	Control register
+ */
+struct i8255 {
+	u8 port[3];
+	u8 control;
+};
+
+/**
+ * struct i8255_state - Intel 8255 state structure
+ * @lock:		synchronization lock for accessing device state
+ * @control_state:	Control register state
+ */
+struct i8255_state {
+	spinlock_t lock;
+	u8 control_state;
+};
+
+void i8255_direction_input(struct i8255 __iomem *ppi, struct i8255_state *state,
+			   unsigned long offset);
+void i8255_direction_output(struct i8255 __iomem *ppi,
+			    struct i8255_state *state, unsigned long offset,
+			    unsigned long value);
+int i8255_get(struct i8255 __iomem *ppi, unsigned long offset);
+int i8255_get_direction(const struct i8255_state *state, unsigned long offset);
+void i8255_get_multiple(struct i8255 __iomem *ppi, const unsigned long *mask,
+			unsigned long *bits, unsigned long ngpio);
+void i8255_mode0_output(struct i8255 __iomem *const ppi);
+void i8255_set(struct i8255 __iomem *ppi, struct i8255_state *state,
+	       unsigned long offset, unsigned long value);
+void i8255_set_multiple(struct i8255 __iomem *ppi, struct i8255_state *state,
+			const unsigned long *mask, const unsigned long *bits,
+			unsigned long ngpio);
+void i8255_state_init(struct i8255_state *const state, unsigned long nbanks);
+
+#endif /* _I8255_H_ */