netfs: zero the tail of a short DIO/unbuffered readgrafted

The buffered read collector zero-fills the tail of a short read that
stops below the inode's i_size (netfs_clear_unread()), so a read that
races an extending write still returns the expected number of bytes.
The non-buffered collector path does no such thing: it just records
how much was transferred.

Add the same zero-fill for the non-buffered case, gated on
NETFS_SREQ_CLEAR_TAIL: a subreq's source sets that flag when a short
result from it is known to be safe to treat as a hole, as opposed to
NETFS_SREQ_HIT_EOF, which means the read genuinely ran off the end of
the file and should be reported short as-is. Only CLEAR_TAIL should
zero-fill here; a real EOF must stay a real short read.

No source currently sets CLEAR_TAIL on an unbuffered/DIO subrequest,
so this is inert on its own -- a following change teaches cifs to set
it in the one case that needs it.

Fixes: e2d46f2ec332 ("netfs: Change the read result collector to only use one work item")
Reviewed-by: David Howells <dhowells@redhat.com>
Reviewed-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Paulo Alcantara <pc@manguebit.org>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Ronnie Sahlberg <ronniesahlberg@gmail.com>
Cc: Shyam Prasad N <sprasad@microsoft.com>
Cc: Tom Talpey <tom@talpey.com>
Cc: Bharath SM <bharathsm@microsoft.com>
Cc: stable@vger.kernel.org

1 files changed, 315 insertions, 0 deletions

diff --git a/drivers/input/touchscreen/penmount.c b/drivers/input/touchscreen/penmount.c
new file mode 100644
index 000000000..4b57b6664
--- /dev/null
+++ b/drivers/input/touchscreen/penmount.c
@@ -0,0 +1,315 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Penmount serial touchscreen driver
+ *
+ * Copyright (c) 2006 Rick Koch <n1gp@hotmail.com>
+ * Copyright (c) 2011 John Sung <penmount.touch@gmail.com>
+ *
+ * Based on ELO driver (drivers/input/touchscreen/elo.c)
+ * Copyright (c) 2004 Vojtech Pavlik
+ */
+
+
+#include <linux/errno.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/input.h>
+#include <linux/input/mt.h>
+#include <linux/serio.h>
+
+#define DRIVER_DESC	"PenMount serial touchscreen driver"
+
+MODULE_AUTHOR("Rick Koch <n1gp@hotmail.com>");
+MODULE_AUTHOR("John Sung <penmount.touch@gmail.com>");
+MODULE_DESCRIPTION(DRIVER_DESC);
+MODULE_LICENSE("GPL");
+
+/*
+ * Definitions & global arrays.
+ */
+
+#define	PM_MAX_LENGTH	6
+#define	PM_MAX_MTSLOT	16
+#define	PM_3000_MTSLOT	2
+#define	PM_6250_MTSLOT	12
+
+/*
+ * Multi-touch slot
+ */
+
+struct mt_slot {
+	unsigned short x, y;
+	bool active; /* is the touch valid? */
+};
+
+/*
+ * Per-touchscreen data.
+ */
+
+struct pm {
+	struct input_dev *dev;
+	struct serio *serio;
+	int idx;
+	unsigned char data[PM_MAX_LENGTH];
+	char phys[32];
+	unsigned char packetsize;
+	unsigned char maxcontacts;
+	struct mt_slot slots[PM_MAX_MTSLOT];
+	void (*parse_packet)(struct pm *);
+};
+
+/*
+ * pm_mtevent() sends mt events and also emulates pointer movement
+ */
+
+static void pm_mtevent(struct pm *pm, struct input_dev *input)
+{
+	int i;
+
+	for (i = 0; i < pm->maxcontacts; ++i) {
+		input_mt_slot(input, i);
+		input_mt_report_slot_state(input, MT_TOOL_FINGER,
+				pm->slots[i].active);
+		if (pm->slots[i].active) {
+			input_event(input, EV_ABS, ABS_MT_POSITION_X, pm->slots[i].x);
+			input_event(input, EV_ABS, ABS_MT_POSITION_Y, pm->slots[i].y);
+		}
+	}
+
+	input_mt_report_pointer_emulation(input, true);
+	input_sync(input);
+}
+
+/*
+ * pm_checkpacket() checks if data packet is valid
+ */
+
+static bool pm_checkpacket(unsigned char *packet)
+{
+	int total = 0;
+	int i;
+
+	for (i = 0; i < 5; i++)
+		total += packet[i];
+
+	return packet[5] == (unsigned char)~(total & 0xff);
+}
+
+static void pm_parse_9000(struct pm *pm)
+{
+	struct input_dev *dev = pm->dev;
+
+	if ((pm->data[0] & 0x80) && pm->packetsize == ++pm->idx) {
+		input_report_abs(dev, ABS_X, pm->data[1] * 128 + pm->data[2]);
+		input_report_abs(dev, ABS_Y, pm->data[3] * 128 + pm->data[4]);
+		input_report_key(dev, BTN_TOUCH, !!(pm->data[0] & 0x40));
+		input_sync(dev);
+		pm->idx = 0;
+	}
+}
+
+static void pm_parse_6000(struct pm *pm)
+{
+	struct input_dev *dev = pm->dev;
+
+	if ((pm->data[0] & 0xbf) == 0x30 && pm->packetsize == ++pm->idx) {
+		if (pm_checkpacket(pm->data)) {
+			input_report_abs(dev, ABS_X,
+					pm->data[2] * 256 + pm->data[1]);
+			input_report_abs(dev, ABS_Y,
+					pm->data[4] * 256 + pm->data[3]);
+			input_report_key(dev, BTN_TOUCH, pm->data[0] & 0x40);
+			input_sync(dev);
+		}
+		pm->idx = 0;
+	}
+}
+
+static void pm_parse_3000(struct pm *pm)
+{
+	struct input_dev *dev = pm->dev;
+
+	if ((pm->data[0] & 0xce) == 0x40 && pm->packetsize == ++pm->idx) {
+		if (pm_checkpacket(pm->data)) {
+			int slotnum = pm->data[0] & 0x0f;
+			pm->slots[slotnum].active = pm->data[0] & 0x30;
+			pm->slots[slotnum].x = pm->data[2] * 256 + pm->data[1];
+			pm->slots[slotnum].y = pm->data[4] * 256 + pm->data[3];
+			pm_mtevent(pm, dev);
+		}
+		pm->idx = 0;
+	}
+}
+
+static void pm_parse_6250(struct pm *pm)
+{
+	struct input_dev *dev = pm->dev;
+
+	if ((pm->data[0] & 0xb0) == 0x30 && pm->packetsize == ++pm->idx) {
+		if (pm_checkpacket(pm->data)) {
+			int slotnum = pm->data[0] & 0x0f;
+			pm->slots[slotnum].active = pm->data[0] & 0x40;
+			pm->slots[slotnum].x = pm->data[2] * 256 + pm->data[1];
+			pm->slots[slotnum].y = pm->data[4] * 256 + pm->data[3];
+			pm_mtevent(pm, dev);
+		}
+		pm->idx = 0;
+	}
+}
+
+static irqreturn_t pm_interrupt(struct serio *serio,
+		unsigned char data, unsigned int flags)
+{
+	struct pm *pm = serio_get_drvdata(serio);
+
+	pm->data[pm->idx] = data;
+
+	pm->parse_packet(pm);
+
+	return IRQ_HANDLED;
+}
+
+/*
+ * pm_disconnect() is the opposite of pm_connect()
+ */
+
+static void pm_disconnect(struct serio *serio)
+{
+	struct pm *pm = serio_get_drvdata(serio);
+
+	serio_close(serio);
+
+	input_unregister_device(pm->dev);
+	kfree(pm);
+
+	serio_set_drvdata(serio, NULL);
+}
+
+/*
+ * pm_connect() is the routine that is called when someone adds a
+ * new serio device that supports PenMount protocol and registers it as
+ * an input device.
+ */
+
+static int pm_connect(struct serio *serio, struct serio_driver *drv)
+{
+	struct pm *pm;
+	struct input_dev *input_dev;
+	int max_x, max_y;
+	int err;
+
+	pm = kzalloc_obj(*pm);
+	input_dev = input_allocate_device();
+	if (!pm || !input_dev) {
+		err = -ENOMEM;
+		goto fail1;
+	}
+
+	pm->serio = serio;
+	pm->dev = input_dev;
+	scnprintf(pm->phys, sizeof(pm->phys), "%s/input0", serio->phys);
+	pm->maxcontacts = 1;
+
+	input_dev->name = "PenMount Serial TouchScreen";
+	input_dev->phys = pm->phys;
+	input_dev->id.bustype = BUS_RS232;
+	input_dev->id.vendor = SERIO_PENMOUNT;
+	input_dev->id.product = 0;
+	input_dev->id.version = 0x0100;
+	input_dev->dev.parent = &serio->dev;
+
+	input_dev->evbit[0] = BIT_MASK(EV_KEY) | BIT_MASK(EV_ABS);
+	input_dev->keybit[BIT_WORD(BTN_TOUCH)] = BIT_MASK(BTN_TOUCH);
+
+	switch (serio->id.id) {
+	default:
+	case 0:
+		pm->packetsize = 5;
+		pm->parse_packet = pm_parse_9000;
+		input_dev->id.product = 0x9000;
+		max_x = max_y = 0x3ff;
+		break;
+
+	case 1:
+		pm->packetsize = 6;
+		pm->parse_packet = pm_parse_6000;
+		input_dev->id.product = 0x6000;
+		max_x = max_y = 0x3ff;
+		break;
+
+	case 2:
+		pm->packetsize = 6;
+		pm->parse_packet = pm_parse_3000;
+		input_dev->id.product = 0x3000;
+		max_x = max_y = 0x7ff;
+		pm->maxcontacts = PM_3000_MTSLOT;
+		break;
+
+	case 3:
+		pm->packetsize = 6;
+		pm->parse_packet = pm_parse_6250;
+		input_dev->id.product = 0x6250;
+		max_x = max_y = 0x3ff;
+		pm->maxcontacts = PM_6250_MTSLOT;
+		break;
+	}
+
+	input_set_abs_params(pm->dev, ABS_X, 0, max_x, 0, 0);
+	input_set_abs_params(pm->dev, ABS_Y, 0, max_y, 0, 0);
+
+	if (pm->maxcontacts > 1) {
+		input_mt_init_slots(pm->dev, pm->maxcontacts, 0);
+		input_set_abs_params(pm->dev,
+				     ABS_MT_POSITION_X, 0, max_x, 0, 0);
+		input_set_abs_params(pm->dev,
+				     ABS_MT_POSITION_Y, 0, max_y, 0, 0);
+	}
+
+	serio_set_drvdata(serio, pm);
+
+	err = serio_open(serio, drv);
+	if (err)
+		goto fail2;
+
+	err = input_register_device(pm->dev);
+	if (err)
+		goto fail3;
+
+	return 0;
+
+ fail3:	serio_close(serio);
+ fail2:	serio_set_drvdata(serio, NULL);
+ fail1:	input_free_device(input_dev);
+	kfree(pm);
+	return err;
+}
+
+/*
+ * The serio driver structure.
+ */
+
+static const struct serio_device_id pm_serio_ids[] = {
+	{
+		.type	= SERIO_RS232,
+		.proto	= SERIO_PENMOUNT,
+		.id	= SERIO_ANY,
+		.extra	= SERIO_ANY,
+	},
+	{ 0 }
+};
+
+MODULE_DEVICE_TABLE(serio, pm_serio_ids);
+
+static struct serio_driver pm_drv = {
+	.driver		= {
+		.name	= "serio-penmount",
+	},
+	.description	= DRIVER_DESC,
+	.id_table	= pm_serio_ids,
+	.interrupt	= pm_interrupt,
+	.connect	= pm_connect,
+	.disconnect	= pm_disconnect,
+};
+
+module_serio_driver(pm_drv);