[Build] DeepGEMM: trim comments, add integration notes + TODOs (#42429)

Signed-off-by: mgoin <mgoin64@gmail.com>

tools/build_deepgemm_C.py

@@ -1,11 +1,10 @@
 # SPDX-License-Identifier: Apache-2.0
 # SPDX-FileCopyrightText: Copyright contributors to the vLLM project
-"""Build DeepGEMM's `_C` pybind11 extension for a target Python.
+"""Build DeepGEMM's `_C` pybind11 extension for <TARGET_PY>.
 
-Driven from `cmake/external_projects/deepgemm.cmake`. The driver is the
-build interpreter (which has torch); the *target* Python is only used for
-its header path and SOABI. This avoids needing torch installed in N venvs
-to produce N matching `.so` files.
+Driven from cmake/external_projects/deepgemm.cmake. The driver runs against
+the build interpreter's torch; <TARGET_PY> is only consulted for INCLUDEPY
+and SOABI, so target venvs don't need torch installed.
 
 Usage: python build_deepgemm_C.py <DEEPGEMM_SRC_DIR> <OUTPUT_DIR> <TARGET_PY>
 """
@@ -42,8 +41,7 @@ info = json.loads(
 cuda_home = cpp_extension.CUDA_HOME
 if cuda_home is None:
     sys.exit("CUDA_HOME not found; cannot build DeepGEMM _C")
-# CCCL lives outside the standard CUDAToolkit search, mirroring DeepGEMM's
-# own setup.py.
+# CCCL lives outside the standard CUDAToolkit search (mirrors DeepGEMM's setup.py).
 includes = [
     info["INCLUDEPY"],
     f"{cuda_home}/include",

tools/setup_deepgemm_pythons.sh

@@ -1,23 +1,12 @@
 #!/usr/bin/env bash
-# Provision bare Python interpreters for the DeepGEMM `_C` per-Python build
-# and print a colon-separated list of their paths to stdout.
-#
-# Each target Python only needs a working interpreter — torch is not
-# installed since `tools/build_deepgemm_C.py` runs from the build interpreter.
-# uv re-uses any matching system Python and downloads a managed build
-# otherwise.
+# Provision one bare Python per `requires-python` entry (or per argument) and
+# print their paths as ":"-separated DEEPGEMM_PYTHON_INTERPRETERS. Skip this
+# entirely if you already have interpreter paths.
 #
 # Usage:
 #   export DEEPGEMM_PYTHON_INTERPRETERS=$(tools/setup_deepgemm_pythons.sh)
 #   python setup.py bdist_wheel --dist-dir=dist --py-limited-api=cp38
 #
-# With no args, expands to every CPython covered by `requires-python` in
-# pyproject.toml. Pass explicit versions (e.g. `3.10 3.11`) to override.
-#
-# Skip this script if you don't have uv: set DEEPGEMM_PYTHON_INTERPRETERS
-# directly to existing interpreter paths. Editable / single-Python builds
-# don't need the env var at all (cmake falls back to the build interpreter).
-#
 # Optional: DEEPGEMM_VENV_PREFIX (default: /tmp/dgenv).
 set -euo pipefail
 
@@ -37,10 +26,8 @@ mkdir -p "$prefix"
 paths=""
 for V in "$@"; do
   venv="$prefix/$V"
-  # Force a managed (uv-downloaded) Python so dev headers are bundled.
-  # System Pythons on the build base may lack headers (manylinux's
-  # /opt/python/cpXY-cpXY are off PATH; an apt-installed python3.X often
-  # has no -dev), and the per-Python build needs Python.h.
+  # uv-managed Python ensures Python.h is present; system 3.X-dev packages
+  # on the manylinux / Ubuntu build bases are not always installed.
   [ -x "$venv/bin/python" ] || \
     uv venv --python "$V" "$venv" --python-preference only-managed --seed \
       >/dev/null